Eur J Pediatr DOI 10.1007/s00431-013-2140-2
ORIGINAL ARTICLE
Anterior cutaneous nerve entrapment syndrome (ACNES): the forgotten diagnosis Samira Akhnikh & Niels de Korte & Peter de Winter
Received: 6 February 2013 / Revised: 30 July 2013 / Accepted: 6 August 2013 # Springer-Verlag Berlin Heidelberg 2013
Abstract The abdominal wall is an often overlooked source of pain in children with chronic abdominal pain. For example, abdominal wall pain can be caused by the abdominal cutaneous nerve entrapment syndrome (ACNES). ACNES occurs in children as well as adults. In pediatrics, this diagnosis is largely unknown. ACNES is characterized by a sharp stabbing pain which characteristically increases with the use of abdominal muscles (Carnett’s sign). The pain is usually located in the lower right quadrant. Very often patient go through a long clinical track, sometimes leading to frequent hospitalizations and unnecessary examinations. In some cases, children even end up in the psychiatric circuit because of misunderstood pain symptoms. We describe three illustrative cases of abdominal pain in which eventually ACNES was diagnosed and successfully treated with infiltration of an anesthetic agent, and we also performed a literature search. Conclusion : ACNES is a relatively unknown cause of abdominal pain in children. Diagnosis and treatment of ACNES are simply by local injection of anesthetics into the abdominal wall. Keywords ACNES . Abdominal cutaneous nerve entrapment syndrome . Abdominal wall pain . Chronic abdominal pain . Children Abbreviations ACNES
Abdominal cutaneous nerve entrapment syndrome
S. Akhnikh (*) : P. de Winter Department of Pediatrics, Spaarne Hospital, Spaarnepoort 1, P.O. Box 770, 2130 AT Hoofddorp, The Netherlands e-mail: [email protected]
Introduction Anterior cutaneous nerve entrapment syndrome (ACNES) is an often overlooked cause of (chronic) abdominal pain. This was first recognized by Carnett and Bates in his seminal article in 1926 [7]. However, nowadays, many physicians are still unaware of this diagnosis. The literature on prevalence of ACNES in the pediatric population is very scarce. Only recently, ACNES has been described in children (Table 1) [12, 15, 17, 18]. Abdominal pain can be classified as visceral pain caused by intra-abdominal organs or parietal pain originating in the abdominal wall. ACNES causes abdominal wall pain, and it is believed that in ACNES, superficial branches of the intercostal thoracic nerves become entrapped between the abdominal muscles and cause pain on this specific location of entrapment. In its presentation, ACNES may therefore mimic an intra-abdominal source of the pain like appendicitis. Carnett first described a test in which the specific point of maximal pain is identified by the investigator after placing patient in supine position. The patient is then asked to raise the head and shoulders. When doing the test right, the abdominal muscles should be contracted. The pain will increase and is pinpointed with a fingertip. Carnett’s sign is then positive, and ACNES becomes more probable (Fig. 1). Pain of visceral origin usually diminishes during this test. Immediate relief of pain after administering a local dose of anesthetic in the rectus sheath at the location of the point of maximal tenderness strongly supports the diagnosis of ACNES, which is also first line in treatment for ACNES. We report three illustrative cases of abdominal pain in children in which eventually ACNES was diagnosed.
P. de Winter e-mail: [email protected]
Patient A
N. de Korte Department of Surgery, Spaarne Hospital, Hoofddorp, The Netherlands
A 15-year-old girl presented to our emergency department with abdominal pain, which had started 3 weeks earlier. The
Eur J Pediatr Table 1 Overview of all articles related to ACNES in children Reference number Number of patients Age Duration of abdominal pain Relapse Number of injections in relapsed patients
[12] 1 11 3.5 months 0 1
[15] 1 15 3 months 0 1
[17] 8 9–16 Unknown All At least two
[18] 7 11–16 4 days–5 months 3 2–3
Current study 3 10–16 1 week–4 months 0 1
Sex
Female
Female
All females
All females
All females
pain was located in the lower right quadrant. There was no apparent provocative moment. She used acetaminophen, but this had no effect on the pain. The blood examination showed a CRP of 70 mg/L; the remainder blood examination was normal. The urinary sediment, pregnancy test, and ultrasound of her abdomen showed no abnormalities. The working diagnosis was gastroenteritis. An appointment for follow-up was made. On follow-up, the stabbing pain was still in the right lower abdomen. She scored an 8 on the Visual Analogue Scale. The physical examination showed a BMI of 28.5 kg/m2 (normal range, 16.1–23.94 kg/m2) and marked tenderness in the right
lower quadrant. Carnett’s test was not performed. Blood examinations showed a CRP level of 36 mg/l. She was admitted to the pediatric ward for observation. The gynecologist conducted a vaginal ultrasound and excluded gynecologic abnormalities. An MRI was conducted and showed only a trace of fluid without any other abnormalities. After 2 days, she was discharged from the hospital. Functional abdominal pain was concluded. Five weeks later, she again presented with the same pain. The pain was progressive, sharp, and stabbing. It increased with the use of abdominal muscles, was most intense during sleep, and was present throughout the day. Furthermore, there was nausea without vomiting. Her general practitioner prescribed acetaminophen combined with tramadol. She was readmitted for observation because of high VAS score and the use of opiates. In addition, we also suspected a psychosocial component. On the second physical examination, tenderness and rebound tenderness in the right lower abdomen were present. Carnett’s test was conducted for the first time and was found positive. ACNES was suspected, and therefore, the departments of anesthesiology, neurology, and surgery were consulted. The anesthesiologist administered an injection with 10 ml Chirocaïne 0.5 % and triamcinolone 40 mg in the rectus sheath at the point of maximum tenderness. A few minutes after treatment, the patient only felt a tender spot at the site of the injection and the sharp pain had resolved. Now after more than 1 year, she is still free of pain.
Patient B
Fig. 1 Carnett’s test. The patient is asked to raise the head and shoulders. When doing the test right, the abdominal muscles should be contracted. The pain will increase and is pinpointed with a fingertip. Carnett’s sign is then positive, and ACNES becomes more probable
The second patient is a 16-year-old girl. She presented herself to the emergency room with abdominal pain that existed for 2 days. The pain was located in the right lower abdomen. She had nausea and a loss of appetite. The medical history showed that she was diagnosed with hypothyroidism and was prescribed with levothyroxine since 1 year. She was also using oral contraceptives, but she was not sexually active. Physical examination showed an obese but not ill-looking girl with a BMI of 32.5 kg/m2 (normal range, 16.6–24.37 kg/ m2). The examination of the abdomen showed tenderness in
Eur J Pediatr
the right lower quadrant. The remainder of the physical examination was normal. Carnett’s test was not conducted. Additional blood tests showed no signs of infection. The abdominal ultrasound showed a slightly enhanced spleen but no other abnormalities. She was re-examined the next day. During re-examination, the pain and nausea had increased but she was still not ill-appearing and there was no fever. The pain still existed in the right lower quadrant. The character of the pain was not known. The remaining physical examination showed no abnormalities. An MRI showed no signs of appendicitis, but the base of the appendix was not easy to assess. She was admitted for observation, and the pediatrician was consulted. To exclude an appendicitis, a diagnostic laparoscopy was performed showing a normal appendix. She was discharged from the hospital after 5 days. During follow-up, her physical conditional and complaints remained the same. The pediatrician was aware of the diagnosis ACNES. The Carnett’s test was positive. The anesthesiologist performed a nerve block using triamcinolone and Chirocaïne. During follow-up and now after 5 months, she remained free of pain.
Patient C The third patient was a 10-year-old girl. She was referred to the surgeon because of abdominal pain in the lower right quadrant since 1 day. Appendicitis was suspected. She had loss of appetite and nausea and vomiting. Defecation was daily and had a normal consistency. The physical examination showed a timid not ill-appearing girl without fever. Palpation of the lower right quadrant was painful. There was contralateral pressure pain and a positive psoas sign. Blood examinations and an ultrasound were conducted and showed no abnormalities. After the examinations, the working diagnosis was constipation and she was given a stool softener. The next day, she was routinely examined at the emergency ward. There were no new leads. She was scheduled to be reexamined the next day. The third day, the pain still existed but appendicitis was excluded. Thereafter, the pediatric physician was consulted. At the fourth presentation, the pain was still located in de right lower quadrant and increased considerably. There was still nausea. The physical examination showed a girl with a BMI of 17.7 kg/m2 (normal range, 13.6–19.86 kg/ m2) and no fever. On physical examination, there was tenderness and rebound tenderness in the lower quadrant. Carnett’s test was not conducted. The pediatrician also concluded constipation. She underwent an enema and was sent home with a stool softener. In the evening, her mother called because the pain was unbearable and she demanded a re-examination. We examined her for the fifth time in 3 days. The physical examination showed a painful girl. Again, there was no fever. Carnett’s test was positive, suggesting ACNES. The anesthesiologist administered Chirocaïne 0.5 % and triamcinolone.
The day of the treatment, she still complained of pain in her abdomen but it had decreased. After 2 days, she was free of pain and now after 8 months, she is still free of pain.
Discussion We report on three almost similar cases of ACNES, illustrating the importance of including this diagnosis in the differential diagnosis. Patient A shows a great delay and excessive additional examinations and was even referred for psychological counseling. Patient B shows extensive additional examinations in just a short period of time, but because of the awareness of the diagnosis, the treatment was given after a short period of abdominal pain. Patient C gives a good indication of how the clinical course can be if ACNES is remembered. All patients were teenage girls. Two girls were overweight; furthermore, there were no similar cofactors or triggers. All patients are thus far free of pain and did not need a second injection. ACNES unfortunately is a relatively unknown diagnosis for abdominal pain. In this article, we try to provide more insight about this simple to diagnose but sometimes difficult to treat syndrome. In a literature search conducted in 2013, we used PubMed, Trip Database, Cochrane Reviews, and Google Scholar and found 53 articles about ACNES in pediatric as well as adult population. Thirty-two were useful. In only four articles, ACNES was described in the pediatric population [12, 15, 17, 18]. The search was done with different keywords: ACNES, anterior cutaneous nerve entrapment syndrome, abdominal cutaneous nerve entrapment syndrome, cutaneous nerve entrapment syndrome, chronic abdominal wall pain, rectus abdominis syndrome, Ibrahim syndrome, intercostal nerve syndrome, and nerve compression syndrome [13]. Cyriax first described abdominal wall pain in 1919 [9]. He described that abdominal wall pain can mimic visceral pain. Between visceral and parietal origin, abdominal wall pain can be distinguished from each other by tensioning the abdomen. Carnett [7] was the first to describe the examination process to differentiate pain of abdominal wall origin from intraabdominal pain in 1926, and he commented on abdominal wall pain being a frequently missed diagnosis [2]. Several articles indicate that pediatricians do not make the distinction between causes from intra-abdominal or the abdominal wall for abdominal pain [3]. The prevalence of ACNES or abdominal wall pain in pediatrics is unknown. In the adult population, there are several articles describing the prevalence from 10 to 30 % of all patients referred to the medical specialist because of chronic abdominal wall pain that are diagnosed with ACNES [14]. More women than men are diagnosed with chronic abdominal
Eur J Pediatr
wall pain, at a ratio of 4:1 [8]. The female/male ratio as regards to ACNES is not described. In the literature, several causes for ACNES are described in the pediatric population like trauma, surgery, and surgical scars or tissue scarring. One case report suggests oral contraceptives as a cause in a 15-year-old girl with ACNES [15]. In the adult population, there are several causes and risk factors mentioned such as physical activity, static or overuse of abdominal wall muscles, obesity, ascites, or pregnancy [13, 16]. The pathoanatomic etiology was first describes by Applegate in 1972 [2]. They performed a microanatomic study and described entrapment of the branches of the relevant intercostal nerves as anatomical base for a cause for abdominal wall pain. The intercostal nerves originate from the nerve roots T8 and T12 (Fig. 2) [1]. The intercostal vein and artery accompany the branch through a fibrous tunnel, the neurovascular bundle. The branches of the intercostal nerves penetrate through the abdominal wall. They penetrate the wall through five foramina on each side of the abdominal rectus muscle, approximately 1 cm medial from to the lateral border of the muscle (Fig. 3). It has been thought that the underlying problem is nerve compression which results in ischemia and lack of blood supply [2, 11].
Fig. 2 The intercostal nerves originate from the nerve roots and the nerve branches penetrating through the rectus abdominis muscle
Fig. 3 Branches of the intercostal nerve penetrating through five foramina on each side of the abdominal rectus muscle, approximately 1 cm medial from to the lateral border of the muscle
The pain due to nerve entrapment is often described as sharp or burning, associated with physical activity, especially with postural changes, localization is in the lower right quadrant of the abdomen, is frequently identified by pressing with one fingertip, and the location of the pain is always at the same spot. Sometimes, there is de-sensibilization of the skin. Other localizations are also described, mostly the lower left quadrant. By palpating the spot, the pain should always increase. It can be continuously present with or without exacerbations or with pain-free intervals [13]. Exacerbations by cramping abdominal pain are described [10]. Nausea, loss of appetite, and vomiting are also associated symptoms with ACNES. However, these symptoms are very nonspecific [18]. Diagnosis as well as treatment of ACNES is done by injecting a local anesthetic by a surgeon or an anesthesiologist. There are several different infusions used in literature, for example, a mixture of 2 ml 0.5 % bupivacaine, 1 ml 1 % lidocaine hydrochloride, 3 mg bethamethasone sodium phosphate and bethamethasone acetate to treat an adolescent girl [15], and an infusion of 5 ml 0.75 % ropivacaine hydrochloride monohydrate and 1 ml of a bethamethasone solution [12]. In our hospital, Chirocaïne 0.5 % and triamcinolone were used. When the pain disappears, the diagnosis ACNES can be confirmed. Although this sounds simple, the treatment can be difficult. The duration of pain relief varies in literature from several hours to complete pain relief [18]. Boelens et al. reported a complete pain reduction after one single dose of lidocaine injection in 20 % of their population and eventually successful treatment of 33 %. Almost 50 % received
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neurectomy of which 71 % reported to be satisfied with the result [6]. It is striking that there was no use of a long-acting steroid like triamcinolone that has an analgesic as well an antiinflammatory effect and creates a better long-term pain relieve response. Scheltinga et al. [17] published in 2011 an article concerning the surgical treatment of refractory ACNES in children. They included eight children in a period of 2.5 years, which were treated with at least two injections with lidocaine and/or methylprednisolone. Eventually, six children had severe recurrent complaints. They underwent anterior neurectomy. After a follow-up of 6 months, all children were free of pain and had resumed their normal daily activity. Recently in 2013, Boelens et al. published two articles concerning treatment in adults. The first article was concerning a singlecenter randomized double-blind placebo-controlled trial. Boelens et al. injected one group with lidocaine and the other with saline. Fifty-four percent of the lidocaine group showed permanent response and 17 % did in the saline group. Boelens et al. concluded that pain reduction was based on anesthetic mechanism and not on a placebo or mechanism (volume) effect [5]. The second trial was doubleblind, randomized controlled on surgery for chronic abdominal pain due to ACNES. Seventy-three percent of patients in the neurectomy group and 18 % in the sham surgery group showed relief of pain. They concluded that neurectomy is an effective surgical procedure for pain reduction in refractory ACNES [4].
Conclusion With these three case reports and review of the literature, we want to remind pediatricians about the existence of abdominal wall as a source of (chronic) abdominal pain in the pediatric population. In literature, ACNES is labeled to be a form of chronic abdominal pain. However, the only reason for its chronic character is because of the lack of knowledge about this form of abdominal wall pain. By raising awareness about ACNES and thereby application of the Carnett’s test, we can prevent unnecessary, invasive, and costly investigation. Moreover, (chronic) abdominal pain has a big impact on a child’s well-being. In different case reports [18, 19] as well as in our patients, the complaints were referred to be from psychosomatic origin. We must underline that even though diagnosing ACNES is simple, the treatment is more difficult.
References 1. Applegate W (2002) Abdominal cutaneous nerve entrapment syndrome: a commonly overlooked cause of abdominal pain. Permanent J 6:20–27 2. Applegate WV (1972) Abdominal cutaneous nerve entrapment syndrome. Surgery 71:118–124 3. Berger M, Gieteling M, Benninga M (2007) Chronic abdominal pain in children. BMJ: Br Med J 334:997 4. Boelens OB, Van Assen T, Houterman S, Scheltinga MR, Roumen RM (2013) A double-blind, randomized, controlled trail on surgery for chronic abdominal pain due to anterior cutaneous nerve entrapment syndrome. Ann Surg 0(0):1–5 5. Boelens OB, Scheltinga MR, Houterman S, Roumen RM (2013) Randomized clinical trial of trigger point infiltration with lidocaine to diagnose anterior cutaneous nerve entrapment syndrome. Br J Surg 2013(100):217–221 6. Boelens OB, Scheltinga MR, Houterman S, Roumen RM (2011) Management of anterior cutaneous nerve entrapment syndrome in a cohort of 139 patients. Ann Surg 254(6):1054 7. Carnett JB, Bates W (1933) The treatment of intercostal neuralgia of the abdominal wall. Ann Surg 98(5):820–829 8. Costanza CD, Longstreth GF, Liu AL (2004) Chronic abdominal wall pain: clinical features, health care costs, and long-term outcome. Clin Gastroenterol Hepatol 2:395–399 9. Cyriax E (1919) On various conditions that may simulate the referred pains of visceral disease, and a consideration of these from the point of view of cause and effect. Practitioner 102:314–322 10. Gray D, Collin J (1987) Non-specific abdominal pain as a cause of acute admission to hospital. Br J Surg 74:239–242 11. Grover M (2013) Chronic abdominal wall pain: a missed diagnosis. http://www.med.unc.edu/ibs/files/educational-gi-handouts/ Chronic%20Abdominal%20Pain.pdf 12. Ivens D, Wojciechowski M, Vaneerdeweg W, Vercauteren M, Ramet J (2008) Abdominal cutaneous nerve entrapment syndrome after blunt abdominal trauma in an 11-year-old girl. J Pediatr Surg 43:e19–e21 13. Lindsetmo RO, Stulberg J (2009) Chronic abdominal wall pain—a diagnostic challenge for the surgeon. Am J Surg 198:129–134 14. McGarrity TJ, Peters DJ, Thompson C, McGarrity SJ (2000) Outcome of patients with chronic abdominal pain referred to chronic pain clinic. Am J Gastroenterol 95:1812–1816 15. Peleg R (1999) Abdominal wall pain caused by cutaneous nerve entrapment in an adolescent girl taking oral contraceptive pills. J Adolesc Health 24:45–47 16. Peleg R, Gohar J, Koretz M, Peleg A (1997) Abdominal wall pain in pregnant women caused by thoracic lateral cutaneous nerve entrapment. Eur J Obstet Gynecol Reprod Biol 74:169–171 17. Scheltinga MR, Boelens OB, Tjon A, Ten WE, Roumen RM (2011) Surgery for refractory anterior cutaneous nerve entrapment syndrome (ACNES) in children. J Pediatr Surg 46:699–703 18. Skinner AV, Lauder GR (2007) Rectus sheath block: successful use in the chronic pain management of pediatric abdominal wall pain. Pediatr Anesth 17:1203–1211 19. Thome J, Egeler C (2006) Abdominal cutaneous nerve entrapment syndrome (ACNES) in a patient with a pain syndrome previously assumed to be of psychiatric origin. World J Biol Psychiatry 7:116–118
ORIGINAL ARTICLE
Anterior cutaneous nerve entrapment syndrome (ACNES): the forgotten diagnosis Samira Akhnikh & Niels de Korte & Peter de Winter
Received: 6 February 2013 / Revised: 30 July 2013 / Accepted: 6 August 2013 # Springer-Verlag Berlin Heidelberg 2013
Abstract The abdominal wall is an often overlooked source of pain in children with chronic abdominal pain. For example, abdominal wall pain can be caused by the abdominal cutaneous nerve entrapment syndrome (ACNES). ACNES occurs in children as well as adults. In pediatrics, this diagnosis is largely unknown. ACNES is characterized by a sharp stabbing pain which characteristically increases with the use of abdominal muscles (Carnett’s sign). The pain is usually located in the lower right quadrant. Very often patient go through a long clinical track, sometimes leading to frequent hospitalizations and unnecessary examinations. In some cases, children even end up in the psychiatric circuit because of misunderstood pain symptoms. We describe three illustrative cases of abdominal pain in which eventually ACNES was diagnosed and successfully treated with infiltration of an anesthetic agent, and we also performed a literature search. Conclusion : ACNES is a relatively unknown cause of abdominal pain in children. Diagnosis and treatment of ACNES are simply by local injection of anesthetics into the abdominal wall. Keywords ACNES . Abdominal cutaneous nerve entrapment syndrome . Abdominal wall pain . Chronic abdominal pain . Children Abbreviations ACNES
Abdominal cutaneous nerve entrapment syndrome
S. Akhnikh (*) : P. de Winter Department of Pediatrics, Spaarne Hospital, Spaarnepoort 1, P.O. Box 770, 2130 AT Hoofddorp, The Netherlands e-mail: [email protected]
Introduction Anterior cutaneous nerve entrapment syndrome (ACNES) is an often overlooked cause of (chronic) abdominal pain. This was first recognized by Carnett and Bates in his seminal article in 1926 [7]. However, nowadays, many physicians are still unaware of this diagnosis. The literature on prevalence of ACNES in the pediatric population is very scarce. Only recently, ACNES has been described in children (Table 1) [12, 15, 17, 18]. Abdominal pain can be classified as visceral pain caused by intra-abdominal organs or parietal pain originating in the abdominal wall. ACNES causes abdominal wall pain, and it is believed that in ACNES, superficial branches of the intercostal thoracic nerves become entrapped between the abdominal muscles and cause pain on this specific location of entrapment. In its presentation, ACNES may therefore mimic an intra-abdominal source of the pain like appendicitis. Carnett first described a test in which the specific point of maximal pain is identified by the investigator after placing patient in supine position. The patient is then asked to raise the head and shoulders. When doing the test right, the abdominal muscles should be contracted. The pain will increase and is pinpointed with a fingertip. Carnett’s sign is then positive, and ACNES becomes more probable (Fig. 1). Pain of visceral origin usually diminishes during this test. Immediate relief of pain after administering a local dose of anesthetic in the rectus sheath at the location of the point of maximal tenderness strongly supports the diagnosis of ACNES, which is also first line in treatment for ACNES. We report three illustrative cases of abdominal pain in children in which eventually ACNES was diagnosed.
P. de Winter e-mail: [email protected]
Patient A
N. de Korte Department of Surgery, Spaarne Hospital, Hoofddorp, The Netherlands
A 15-year-old girl presented to our emergency department with abdominal pain, which had started 3 weeks earlier. The
Eur J Pediatr Table 1 Overview of all articles related to ACNES in children Reference number Number of patients Age Duration of abdominal pain Relapse Number of injections in relapsed patients
[12] 1 11 3.5 months 0 1
[15] 1 15 3 months 0 1
[17] 8 9–16 Unknown All At least two
[18] 7 11–16 4 days–5 months 3 2–3
Current study 3 10–16 1 week–4 months 0 1
Sex
Female
Female
All females
All females
All females
pain was located in the lower right quadrant. There was no apparent provocative moment. She used acetaminophen, but this had no effect on the pain. The blood examination showed a CRP of 70 mg/L; the remainder blood examination was normal. The urinary sediment, pregnancy test, and ultrasound of her abdomen showed no abnormalities. The working diagnosis was gastroenteritis. An appointment for follow-up was made. On follow-up, the stabbing pain was still in the right lower abdomen. She scored an 8 on the Visual Analogue Scale. The physical examination showed a BMI of 28.5 kg/m2 (normal range, 16.1–23.94 kg/m2) and marked tenderness in the right
lower quadrant. Carnett’s test was not performed. Blood examinations showed a CRP level of 36 mg/l. She was admitted to the pediatric ward for observation. The gynecologist conducted a vaginal ultrasound and excluded gynecologic abnormalities. An MRI was conducted and showed only a trace of fluid without any other abnormalities. After 2 days, she was discharged from the hospital. Functional abdominal pain was concluded. Five weeks later, she again presented with the same pain. The pain was progressive, sharp, and stabbing. It increased with the use of abdominal muscles, was most intense during sleep, and was present throughout the day. Furthermore, there was nausea without vomiting. Her general practitioner prescribed acetaminophen combined with tramadol. She was readmitted for observation because of high VAS score and the use of opiates. In addition, we also suspected a psychosocial component. On the second physical examination, tenderness and rebound tenderness in the right lower abdomen were present. Carnett’s test was conducted for the first time and was found positive. ACNES was suspected, and therefore, the departments of anesthesiology, neurology, and surgery were consulted. The anesthesiologist administered an injection with 10 ml Chirocaïne 0.5 % and triamcinolone 40 mg in the rectus sheath at the point of maximum tenderness. A few minutes after treatment, the patient only felt a tender spot at the site of the injection and the sharp pain had resolved. Now after more than 1 year, she is still free of pain.
Patient B
Fig. 1 Carnett’s test. The patient is asked to raise the head and shoulders. When doing the test right, the abdominal muscles should be contracted. The pain will increase and is pinpointed with a fingertip. Carnett’s sign is then positive, and ACNES becomes more probable
The second patient is a 16-year-old girl. She presented herself to the emergency room with abdominal pain that existed for 2 days. The pain was located in the right lower abdomen. She had nausea and a loss of appetite. The medical history showed that she was diagnosed with hypothyroidism and was prescribed with levothyroxine since 1 year. She was also using oral contraceptives, but she was not sexually active. Physical examination showed an obese but not ill-looking girl with a BMI of 32.5 kg/m2 (normal range, 16.6–24.37 kg/ m2). The examination of the abdomen showed tenderness in
Eur J Pediatr
the right lower quadrant. The remainder of the physical examination was normal. Carnett’s test was not conducted. Additional blood tests showed no signs of infection. The abdominal ultrasound showed a slightly enhanced spleen but no other abnormalities. She was re-examined the next day. During re-examination, the pain and nausea had increased but she was still not ill-appearing and there was no fever. The pain still existed in the right lower quadrant. The character of the pain was not known. The remaining physical examination showed no abnormalities. An MRI showed no signs of appendicitis, but the base of the appendix was not easy to assess. She was admitted for observation, and the pediatrician was consulted. To exclude an appendicitis, a diagnostic laparoscopy was performed showing a normal appendix. She was discharged from the hospital after 5 days. During follow-up, her physical conditional and complaints remained the same. The pediatrician was aware of the diagnosis ACNES. The Carnett’s test was positive. The anesthesiologist performed a nerve block using triamcinolone and Chirocaïne. During follow-up and now after 5 months, she remained free of pain.
Patient C The third patient was a 10-year-old girl. She was referred to the surgeon because of abdominal pain in the lower right quadrant since 1 day. Appendicitis was suspected. She had loss of appetite and nausea and vomiting. Defecation was daily and had a normal consistency. The physical examination showed a timid not ill-appearing girl without fever. Palpation of the lower right quadrant was painful. There was contralateral pressure pain and a positive psoas sign. Blood examinations and an ultrasound were conducted and showed no abnormalities. After the examinations, the working diagnosis was constipation and she was given a stool softener. The next day, she was routinely examined at the emergency ward. There were no new leads. She was scheduled to be reexamined the next day. The third day, the pain still existed but appendicitis was excluded. Thereafter, the pediatric physician was consulted. At the fourth presentation, the pain was still located in de right lower quadrant and increased considerably. There was still nausea. The physical examination showed a girl with a BMI of 17.7 kg/m2 (normal range, 13.6–19.86 kg/ m2) and no fever. On physical examination, there was tenderness and rebound tenderness in the lower quadrant. Carnett’s test was not conducted. The pediatrician also concluded constipation. She underwent an enema and was sent home with a stool softener. In the evening, her mother called because the pain was unbearable and she demanded a re-examination. We examined her for the fifth time in 3 days. The physical examination showed a painful girl. Again, there was no fever. Carnett’s test was positive, suggesting ACNES. The anesthesiologist administered Chirocaïne 0.5 % and triamcinolone.
The day of the treatment, she still complained of pain in her abdomen but it had decreased. After 2 days, she was free of pain and now after 8 months, she is still free of pain.
Discussion We report on three almost similar cases of ACNES, illustrating the importance of including this diagnosis in the differential diagnosis. Patient A shows a great delay and excessive additional examinations and was even referred for psychological counseling. Patient B shows extensive additional examinations in just a short period of time, but because of the awareness of the diagnosis, the treatment was given after a short period of abdominal pain. Patient C gives a good indication of how the clinical course can be if ACNES is remembered. All patients were teenage girls. Two girls were overweight; furthermore, there were no similar cofactors or triggers. All patients are thus far free of pain and did not need a second injection. ACNES unfortunately is a relatively unknown diagnosis for abdominal pain. In this article, we try to provide more insight about this simple to diagnose but sometimes difficult to treat syndrome. In a literature search conducted in 2013, we used PubMed, Trip Database, Cochrane Reviews, and Google Scholar and found 53 articles about ACNES in pediatric as well as adult population. Thirty-two were useful. In only four articles, ACNES was described in the pediatric population [12, 15, 17, 18]. The search was done with different keywords: ACNES, anterior cutaneous nerve entrapment syndrome, abdominal cutaneous nerve entrapment syndrome, cutaneous nerve entrapment syndrome, chronic abdominal wall pain, rectus abdominis syndrome, Ibrahim syndrome, intercostal nerve syndrome, and nerve compression syndrome [13]. Cyriax first described abdominal wall pain in 1919 [9]. He described that abdominal wall pain can mimic visceral pain. Between visceral and parietal origin, abdominal wall pain can be distinguished from each other by tensioning the abdomen. Carnett [7] was the first to describe the examination process to differentiate pain of abdominal wall origin from intraabdominal pain in 1926, and he commented on abdominal wall pain being a frequently missed diagnosis [2]. Several articles indicate that pediatricians do not make the distinction between causes from intra-abdominal or the abdominal wall for abdominal pain [3]. The prevalence of ACNES or abdominal wall pain in pediatrics is unknown. In the adult population, there are several articles describing the prevalence from 10 to 30 % of all patients referred to the medical specialist because of chronic abdominal wall pain that are diagnosed with ACNES [14]. More women than men are diagnosed with chronic abdominal
Eur J Pediatr
wall pain, at a ratio of 4:1 [8]. The female/male ratio as regards to ACNES is not described. In the literature, several causes for ACNES are described in the pediatric population like trauma, surgery, and surgical scars or tissue scarring. One case report suggests oral contraceptives as a cause in a 15-year-old girl with ACNES [15]. In the adult population, there are several causes and risk factors mentioned such as physical activity, static or overuse of abdominal wall muscles, obesity, ascites, or pregnancy [13, 16]. The pathoanatomic etiology was first describes by Applegate in 1972 [2]. They performed a microanatomic study and described entrapment of the branches of the relevant intercostal nerves as anatomical base for a cause for abdominal wall pain. The intercostal nerves originate from the nerve roots T8 and T12 (Fig. 2) [1]. The intercostal vein and artery accompany the branch through a fibrous tunnel, the neurovascular bundle. The branches of the intercostal nerves penetrate through the abdominal wall. They penetrate the wall through five foramina on each side of the abdominal rectus muscle, approximately 1 cm medial from to the lateral border of the muscle (Fig. 3). It has been thought that the underlying problem is nerve compression which results in ischemia and lack of blood supply [2, 11].
Fig. 2 The intercostal nerves originate from the nerve roots and the nerve branches penetrating through the rectus abdominis muscle
Fig. 3 Branches of the intercostal nerve penetrating through five foramina on each side of the abdominal rectus muscle, approximately 1 cm medial from to the lateral border of the muscle
The pain due to nerve entrapment is often described as sharp or burning, associated with physical activity, especially with postural changes, localization is in the lower right quadrant of the abdomen, is frequently identified by pressing with one fingertip, and the location of the pain is always at the same spot. Sometimes, there is de-sensibilization of the skin. Other localizations are also described, mostly the lower left quadrant. By palpating the spot, the pain should always increase. It can be continuously present with or without exacerbations or with pain-free intervals [13]. Exacerbations by cramping abdominal pain are described [10]. Nausea, loss of appetite, and vomiting are also associated symptoms with ACNES. However, these symptoms are very nonspecific [18]. Diagnosis as well as treatment of ACNES is done by injecting a local anesthetic by a surgeon or an anesthesiologist. There are several different infusions used in literature, for example, a mixture of 2 ml 0.5 % bupivacaine, 1 ml 1 % lidocaine hydrochloride, 3 mg bethamethasone sodium phosphate and bethamethasone acetate to treat an adolescent girl [15], and an infusion of 5 ml 0.75 % ropivacaine hydrochloride monohydrate and 1 ml of a bethamethasone solution [12]. In our hospital, Chirocaïne 0.5 % and triamcinolone were used. When the pain disappears, the diagnosis ACNES can be confirmed. Although this sounds simple, the treatment can be difficult. The duration of pain relief varies in literature from several hours to complete pain relief [18]. Boelens et al. reported a complete pain reduction after one single dose of lidocaine injection in 20 % of their population and eventually successful treatment of 33 %. Almost 50 % received
Eur J Pediatr
neurectomy of which 71 % reported to be satisfied with the result [6]. It is striking that there was no use of a long-acting steroid like triamcinolone that has an analgesic as well an antiinflammatory effect and creates a better long-term pain relieve response. Scheltinga et al. [17] published in 2011 an article concerning the surgical treatment of refractory ACNES in children. They included eight children in a period of 2.5 years, which were treated with at least two injections with lidocaine and/or methylprednisolone. Eventually, six children had severe recurrent complaints. They underwent anterior neurectomy. After a follow-up of 6 months, all children were free of pain and had resumed their normal daily activity. Recently in 2013, Boelens et al. published two articles concerning treatment in adults. The first article was concerning a singlecenter randomized double-blind placebo-controlled trial. Boelens et al. injected one group with lidocaine and the other with saline. Fifty-four percent of the lidocaine group showed permanent response and 17 % did in the saline group. Boelens et al. concluded that pain reduction was based on anesthetic mechanism and not on a placebo or mechanism (volume) effect [5]. The second trial was doubleblind, randomized controlled on surgery for chronic abdominal pain due to ACNES. Seventy-three percent of patients in the neurectomy group and 18 % in the sham surgery group showed relief of pain. They concluded that neurectomy is an effective surgical procedure for pain reduction in refractory ACNES [4].
Conclusion With these three case reports and review of the literature, we want to remind pediatricians about the existence of abdominal wall as a source of (chronic) abdominal pain in the pediatric population. In literature, ACNES is labeled to be a form of chronic abdominal pain. However, the only reason for its chronic character is because of the lack of knowledge about this form of abdominal wall pain. By raising awareness about ACNES and thereby application of the Carnett’s test, we can prevent unnecessary, invasive, and costly investigation. Moreover, (chronic) abdominal pain has a big impact on a child’s well-being. In different case reports [18, 19] as well as in our patients, the complaints were referred to be from psychosomatic origin. We must underline that even though diagnosing ACNES is simple, the treatment is more difficult.
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