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275

Sonographic Perforation Appendicitis

Karen F. Borushok1 R. Brooke Jeffrey, Jr.2 Faye C. Laing1 Ronald R. Townsend1

Diagnosis in Patients

of with Acute

The sonographic diagnosis of appendicitis can be challenging in patients with perleration. In order to detect the accuracy of specific sonographic features of appendiceal

perforation,

graded

compression

sonograms

in 100 patients

with surgically

confirmed

acute appendicitis were reviewed retrospectively. Twenty-two of these patients had perforation. A statistically significant association was found between three sonographic findings and perforation: loculated pericecal fluid, prominent pencecal fat, and circumferential loss of the submucosal layer of the appendix. No single finding had a specificity greater than 59% By using a combination of one or more findings, the overall sensitivity of sonography for the diagnosis of perforation was 86%. The specificity, however, was only

60%.

Our

results

recognition

indirect AJR

suggest

that

of loculated

in

without

a sonographically

fluid and prominent of perforating appendicitis.

clue to the diagnosis 154:275-278,

patients

pencecal

visible

pencecal

fat may

appendix,

be a useful

1990

February

Graded compression sonography has been proved to be of value in the diagnosis of acute appendicitis, with sensitivities ranging from 75% to 89% [1 -5]. The sonographic diagnosis of appendicitis may be difficult, however, in patients with perforation. Puylaert et al. [4] reported a sensitivity of only 29% in patients with perforating appendicitis in a recent prospective study. In addition, there are no reports of specific criteria that can be used to diagnose a perforated appendix sonographically.

On the basis of our prior clinical experience in suspected

appeared

acute

appendicitis,

Materials

and

Califomia, San Francisco, San Francisco General Hospital, 1001 Potrero Ave., San Francisco, CA 94110. 2 Department

of Diagnostic

Stanford University CA 94305. Address frey, Jr.

Schcol reprint

Radiology

(Hi 307),

of Medicine, Stanford, requests to R. B. Jef-

0361 -803X/90/i 542-0275 © American Roentgen Ray Society

that

retrospective

several

perforating

to analyze

sonography

sonographic

features

from nonperforating

the sonographic

findings

that

appendi-

associated

with

Methods

From February sonography

with graded compression

noted

to be of value in differentiating

citis. In this report, we attempt appendiceal perforation.

Received August 21 , 1 989; accepted after revision September 22, 1989. 1 Department of Radiology (1X55), University of

we

1986 to May 1989, showed

review

acute

100 patients

appendicitis

of the sonographic

and

and

who had both graded

surgical

pathologic

confirmation

findings.

Overall,

compression

were

selected

there

were

for

a

69 males

and 31 females, ranging in age from 1 to 71 years (mean, 29 years). Among the 22 patients with

perforating

appendicitis,

there

were

68 years (mean, 27 years). All sonographic focused

linear-array

transducer

(Acuson,

1 6 males

and

6 females,

studies were obtained Sunnyvale,

CA)

by

ranging

in age

from

1 to

with a 5-MHz electronically using

the

real-time

graded

compression technique described by Puylaert [1]. The sonographic criteria established by Jeffrey et al. [3] were used to diagnose acute appendicitis in this series. Patients with a noncompressible

acute appendicitis. ically

appendix

7 mm

or more

The only exception

visible appendicolith.

If an

in maximal

outer

to the size criterion

appendicolith

diameter

were

was in patients

was present,

considered

to have

with a sonograph-

the patient was considered

to

BORUSHOK

276

TABLE

1: Sonographic

Sonographic

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Statistically

Findings

Finding significant

in Appendiceal

True-Positive

True-Negative

13

250

36.4

78.2

6 16

56 22

22 56

16 6

>750 >750

27.3 72.7

71.8 28.2

19

47

31

3

86.4

60.3

noting

the

presence

of perforation,

appendiceal

size,

appendicoliths, and final pathologic diagnosis. Final pathologic diagnoses were either uncomplicated acute suppurative appendicitis or with

Sensitivity

40.9

have acute appendicitis regardless of the size of the appendix. Surgery was performed within 48 hr of sonography in all patients. Pathologic reports of the appendiceal specimens were reviewed

appendicitis

p Value

0

of All Find-

retrospectively,

False-Negative

False-Positive

78

Not statistically significant for perforation Appendicohiths Focal loss of submucosal layer of appendix Retrocecal location of appendix Free pericecal fluid Maximal outer wall diameter of appendix 1O mm Percentage ings

Perforation

9

pericecal

>10 mm Circumferential submucosal appendix

AJR:154, February 1990

for

perforation Loculated pericecal fluid Prominent

ET AL.

perforation.

Surgical

reports

also

were

used

to

these pathologic diagnoses. There were 22 patients with perforating and 78 patients with nonperforating appendicitis. Chisquare analysis with Yates correction, or Student’s t test, was used to evaluate each of the sonographic features for perforation (see Table 1). The sonographic studies were reviewed retrospectively in a blinded

tions,

and

appendicoliths.

The

0

following

specific

sonographic

features

were analyzed: (1 ) lack of visualization of the echogenic submucosal layer (either focal or circumferential) (Figs. 1 and 2), (2) presence or absence of appendicoliths, (3) pericecal free fluid, (4) pericecal loculated fluid (Fig. 3), (5) pericecal echogenic fat more than 10 mm thick (Fig. 1), and (6) marked enlargement of the appendix with maximal outer appendiceal diameters of greater than or equal to 10 mm.

confirm

fashion

without

knowledge

of whether

there was appendiceal

perfo-

ration. Transverse and longitudinal sonographic images of the appendix and pericecal area were analyzed for evidence of transmural appendiceal

marked

inflammation,

enlargement

periappendiceal

of the appendix,

inflammatory

free or loculated

reaction,

fluid collec-

Results

Only three sonographic

findings

were statistically

significant

for the diagnosis of perforating appendicitis: loculated pencecal fluid (p < .001), circumferential loss of the echogenic submucosal layer of the appendix (p < .05), and prominent adjacent penicecal fat more than 1 0 mm thick (p < .01). The remaining sonographic findings were not statistically signifi-

cant in discriminating

between

perforating

and nonperforating

Fig. 1.-Perforating appendicitis with CT correlation. A, Sagittal sonogram shows a noncompressible appendix with an appendicolith (curved arrow). Note linear echogenic appearance of preserved submucosal layer (large straight arrow) and focal areas of interruption of submucosa (small straight arrows). Note prominent fat (arrowheads) surrounding perforated appendix. B, CT scan of same patient shows calcified appendicolith (black arrow) and surrounding edematous periappendiceal fat (white arrows).

AJR:154,

February

1990

SONOGRAPHY

OF

ACUTE

APPENDICITIS

277

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Fig. 2.-Perforated appendix (A) with circumferential loss of echogenic submucosa on sagittal sonogram. Note prominent periappendiceal fat (arrows). C = cecum.

Fig. 3.-Perforated appendix with loculated fluid (abscess). Sonogram shows rounded collection of complex fluid containing low-level echoes. Note surrounding echogenic fat (arrows) “walling off” abscess.

appendicitis. The best single sonographic feature for diagnosing appendiceal perforation was detecting a loculated pericecal fluid collection indicating an abscess. However, this finding was visualized in only nine of 22 perforated appendices (sensitivity, 4i%) but was not visualized in any of the 78 nonperforated cases (specificity, 100%). By using a combination of one or more of the statistically significant findings, the overall sensitivity for the sonographic diagnosis of perforation was 86%, with a specificity of 60%.

Discussion

Graded compression sonography is of value in the clinical diagnosis of acute appendicitis. However, the recently reported low sensitivity of 29% for diagnosing appendicitis in patients with perforation suggests a relative limitation of this technique [4]. It is likely that focal peritonitis associated with perforation may lead to inadequate compression or that extensive necrosis of the appendix renders it difficult to visualize. In reports of large numbers of cases, the rate of appendiceal perforation ranges from 1 3% to 31 %, with rates as high as 65% accuracy in the elderly [6-i 1]. In a review of 1000 patients from our institution who underwent appendectomy before graded compression sonography, the overall perforation rate was 21 %, virtually identical to the 22% rate noted in this series [6]. Puylaert et al. [4] have suggested that failure to diagnose appendiceal perforation by sonography rarely affects treatment of patients. This is certainly true in patients with small perforations, because prompt appendectomy is warranted. A review of the surgical literature, however, suggests that the need for immediate surgery is controversial in patients with perforating appendicitis and large peniappendiceal inflammatory masses. Early surgery in some patients may be associated with higher morbidity than conservative management [1 2-i 5]. In patients with large peniappendiceal phlegmons, antibiotic therapy followed by interval appendectomy is an acceptable alternative to immediate surgery [1 6]. In patients with well-defined and well-localized periappendiceal abscesses, percutaneous catheter drainage followed by interval

appendectomy also can be performed with low morbidity [16, 1 7]. Thus, the failure to diagnose perforating appendicitis by sonography may lead to inappropriate early surgery when conservative management or percutaneous drainage would have been preferable. To date, little analysis of specific sonographic features of appendiceal perforation has been done. Puylaert noted that atonic bowel loops, intenloop fluid pockets, thickened bowel walls, moderate amounts of free fluid, and no tenderness when pressure is applied to the right lower quadrant may be identified in various degrees in patients with perforating appendicitis [1]. The ultimate usefulness of these findings is limited by the lack of statistical analysis and documentation of their occurrence in patients with appendicitis without perforation. Three sonographic findings (loculated fluid, prominent pencecal fat, and circumferential loss of the echogenic layer of appendiceal submucosa) were all statistically associated with appendiceal perforation. No single finding had a sensitivity for perforation greater than 59%. With a combination of one or more findings, however, the sensitivity increased to 84%, but the specificity was only 60%. Recent anatomic studies correlating the sonographic appearance of layers of the bowel wall show that the submucosal layer can readily be identified sonographically and that it is echogenic [1 8]. Although not specifically proved by our data, the lack of sonognaphic visualization of the echogenic submucosal layer is likely to represent extensive submucosal ulceration and necrosis that can be correlated statistically with a greater likelihood of perforation. No statistically significant correlation was seen between sonographic edema of free fluid and the presence of perforation. Neither the presence of an appendicohith or marked enlargement of the appendix (>1 0 mm) was associated with perforation. In adults, appendiceal perforation is often contained and “walled off” by adjacent omental and mesenteric fat, thus preventing generalized peritonitis [1 6] (Fig. 3). With contrastenhanced CT, peniappendiceal inflammatory masses are often composed primarily of inflamed omental and mesenteric fat [1 6] (Fig. i). Thus, prominent penicecal fat may be indirect

BORUSHOK

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278

evidence of appendiceal perforation with evolution of a periappendiceal phlegmon. This sonographic finding will be of limited use in patients with little omental or mesenteric fat. We also have observed, anecdotally, prominent omental fat in patients with other diseases causing transmural inflammation of the bowel such as cecal diverticuhitis. Thus, this finding is not specific for perforating appendicitis. The most specific sonographic feature of appendiceal perforation in this series was the presence of loculated pericecal fluid, indicating an abscess. Loculated fluid collections often appeared rounded in configuration and cause a mass effect on adjacent bowel loops (Fig. 3). Free fluid in the right lower quadrant, on the other hand, is nonspecific and may be seen in patients without appendicitis. It is often triangular in configuration as it passively conforms to the paracolic gutter. In patients with sonographic findings suggestive of appendicitis, the visualization of a loculated penicecal fluid collection was 1 00% specific for perforation in our series. The sensitivity,

however,

was only 41%.

Recognition

of the

sonographic

findings

associated

with

appendiceal perforation is important for two reasons. First, in patients without an initially visible, noncompressible appendix, identification of prominent penicecal fat and/or loculated pericecal fluid may be an important indirect clue to the diagnosis of underlying appendicitis. Thus, further efforts to show the

appendix

are warranted.

When specific

attention

is directed

toward imaging of the prominent penicecal fat, remnants of a perforated appendix can be recognized surrounded by the echogenic fatty mass. The ultimate specificity of prominent pericecal fat and loculated fluid alone, without a sonographically visible appendix, must await a prospective study. Second, patients with appendiceal perforation and a large

abscess

or phlegmon

may be managed

with antibiotics

and/

or with percutaneous drainage. Contrast-enhanced CT is the imaging method of choice to characterize peniappendiceal inflammatory masses [1 6]. CT can be used readily to distinguish areas of hiquified abscess from phlegmon and to guide percutaneous catheter drainage [16]. On the basis of the CT findings, the surgeon can make an informed decision regarding either early surgery, primary antibiotic therapy, or percu-

ET

AL.

taneous drainage. Sonography of patients for further evaluation

AJR:154, February 1990

may then help in the selection with CT.

REFERENCES 1 . Puylaert JCBM. Acute appendicitis: US evaluation using graded compression. Radiology 1986;i58:355-360 2. Jeffrey RB, Laing FC, Lewis FR. Acute appendicitis: high resolution realtime US findings. Radiology 1987;163: 11-14 3. Jeffrey RB, Laing FC, Townsend RR. Acute appendicitis: sonographic criteria based on 250 cases. Radiology 1988;167:327-329 4. Puylaert JCBM, Rutgers PH, Lalisang RI, et al. A prospective study of ultrasonography in the diagnosis of appendicitis. N EngI J Med 1987; 317:666-669 5. Abu-Yousef MM, BleicherJJ, MaherJW, Urdaneta LF, Franken EA, Metcalf AM. High-resolution sonography of acute appendicitis. AJR 1987;149: 53-58 6. Lewis FR, Holcroft JW, Boey J, Dunphy JE. Appendicitis: a critical review of diagnosis and treatment in 1 000 cases. Arch Surg 1975;1 10:677-684 7. Detmer DE, Nevers LE, Sikes ED. Regional results of acute appendicitis care. JAMA 1981;246:1318-1320 8. Ricci MA, Cuasay RS, Beck WC. Appendicitis: the perforation rate when reviewed by decades in a general hospital. Am Surg 1988;54:273-275 9. McCallion J, Canning GP, Knight PV, McCallion JS. Acute appendicitis in the elderly: a 5-year retrospective study. Age and Ageing 1987;1 6: 256-260 10. Berry J, Malt RA. Appendicitis nears its centenary. Ann Surg 1984;200: 567-575 1 1 . Peltokallio P. Tykka H. Evolution in the age distribution and mortality of acute appendicitis. Arch Surg 1981;1 16: 153-1 56 12. Skoubo-Kristensen E, Hvid I. The appendiceal mass: conservative management. Ann Surg 1982;196:584-587 13. Hoffman J, Lindhard A, Jensen HE. Appendix mass: results of conservative management without interval appendectomy. Am J Surg 1984;148: 379-382 14. Bagi P. Dueholm S. Nonoperative management of the ultrasonically evaluated appendiceal mass. Surgery 1987:101:602-605 15. Paull DL, Bloom GP. Appendiceal abscess. Arch Surg 1982;1 17: 101 7-1 019 16. Jeffrey RB, Tolentino CS, Federle MP, Laing FC. Percutaneous drainage of periappendiceal abscesses: review of 20 patients. AJR 1987;149: 59-62 1 7. Jeffrey RB, Federle MP, Tolentino CS. Periappendiceal inflammatory masses: CT-directed management and clinical outcome in 70 patients. Radiology 1988;167: 13-16 18. Kimmey MB, Martin RW, Hagitt RC, Wang KY, Franklin DW, Silverstein FE. Histologic correlates of gastrointestinal ultrasound images. Gastroenterology 1989;96:433-441