Congenital Diaphragmatic Hernia: The Hidden Mortality By Michael R. Harrison, Roald I. Bjordal, FrCydis Langmark, and O. Knutrud 9 From 1969 to 1975, 33 cases of congenital diaphragmatic hernia (CDH) were treated at the National Hospital of Norway with a "visible" or operative mortality of 30%. At least 37 additional infants with C D H w h o died soon after birth and did not come to the attention of a major referral center were identified retrospectively from a comprehensive survey of neonatal deaths. C D H occurred at least once in every 5 4 5 5 live births and the "true" mortality was 66%. More than half of the infants born with C D H during this 6-yr period died before they could be treated, contributing to a substantial "hidden" mortality. I N D E X W O R D S : Congenital diaphragmatic hernia.

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COMPREHENSIVE survey of neonatal deaths in Norway from 1969 to 1975 revealed many more cases of congenital diaphragmatic hernia (CDH) than were recognized and treated at the country's major referral center, the National Hospital of Norway (Rikshospital), during the same 6-yr period. This obvious discrepancy prompted an analysis of the incidence and mortality of CDH in a well-defined national population with a welldocumented birth rate. MATERIALS AND METHODS "Visible" incidence and mortality is based on the number of cases of CDH recognized clinically in Norway from 1969 to 1975 and treated at a major referral center. Virtually all neonates with emergent surgical anomalies recognized in Norway (population 4 million) are transported to one major pediatric surgical service at the Rikshospital in Oslo. Thirty-three cases of CDH seen at the Rikshospital from 1969 to 1975 were reviewed. Surveys of other major surgical centers in Norway revealed no further cases of CDH during this period. Since 1969, all infant deaths in Norway have been recorded by cause of death, sex, and age. From 1969 to 1975, 46 fatal cases of CDH were recorded, including nine operated upon at the Rikshospital. Analysis of these data provided a minimum estimate of the "true" incidence of CDH in the population. "True" incidence and mortality is based on the total number of cases detected in Norway from 1969 to 1975, including 37 cases not recognized clinically but reported in a survey of neonatal deaths. Population, birth rate, and infant mortality data were obtained from the Central Statistical Office of Norway. The 33 cases of CDH treated at the Rikshospital were reviewed for mortality factors and associated anomalies. In addition, autopsy material from 15 cases of CDH treated at the Rikshospital since 1959 was reviewed. Lung weights were tabulated and compared to expected normal lung

Journal of Pediatric Surgery, VoI. 13, No. 3 (June), 1978

weight for that developmental age and weight, and associated anomalies were recorded. RESULTS

Incidence T h e n u m b e r o f c a s e s (33) t r e a t e d in a m a j o r p e d i a t r i c s u r g i c a l c e n t e r is less t h a n h a l f o f t h e t o t a l c a s e s (70) r e c o g n i z e d r e t r o s p e c t i v e l y , i.e., t h e " v i s i b l e " i n c i d e n c e is less t h a n h a l f o f t h e "true" incidence. Tables 1 and 2 summarize the d a t a . T h e " t r u e " i n c i d e n c e o f 11.5 c a s e s / y r for a p o p u l a t i o n o f 4 million o r 1/5455 live b i r t h s is a solid m i n i m u m e s t i m a t e o f t r u e i n c i d e n c e . It is a m i n i m u m e s t i m a t e b e c a u s e : (1) a b o r t e d and s t i l l b o r n f e t u s e s a r e n o t r e l i a b l y i n c l u d e d in t h e s u r v e y d a t a ; (2) n o t all n e o n a t a l d e a t h s a r e d i a g n o s e d by x - r a y o r by a u t o p s y , a n d (3) d i a p h r a g m a t i c h e r n i a s r e c o g n i z e d l a t e r in life and h i a t a l h e r n i a s a r e a r b i t r a r i l y e x c l u d e d f r o m this s t u d y .

Mortality More than half (37 of 70) of the infants with CDH died u n t r e a t e d (Table 1). Detailed analysis of the 37 infants who died without coming to the attention of the major referral center was not possible from available data. Mortality factors other than the presence of CDH (associated anomalies, severity of respiratory symptoms, gestational age) could not be determined. However, most of these infants died soon after birth; 34 of 37 before 24 hr of age, (9 of the 12 deaths that occurred after 24 hr of age in the neonatal mortality survey were infants treated at the Rikshospital). Although it is not possible to determine if any of these 37 infants From the Departments of Pediatric Surgery and Pathology, The National Hospital of Norway, Oslo, Norway and the Department of Surgery, Childrens Hospital of Los Angeles, Los Angeles, Calif. Presented before the 26th Annual Meeting of the American Academy of Pediatrics, Surgical Section, New York, New York, November6-8, 1977. Address reprint requests to Michael Harrison, M.D., Childrens Hospital of Los Angeles, P.O. Box 54700, Los Angeles, Calif. 90054. 9 1978 by Grune & Stratton, Inc. 0022-3468/78/ 1303-0004501.00/0 227

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HARRISON ET AL.

Table 1. Congenital Diaphragmatic Hernia in Norway ( 1 9 6 9 - 1 9 7 5 )

1969

1970

1971

Year 1972

1973

1974

6-Yr Totals

6 (O)t

5 (1)

4 (2)

7 (3)

7 (3)

4 (1)

33 (10)

Cases recognized postmortemS: Died < 24 hours Died 1-7 days Died > 7 days Total cases recognized

5 1 0 12

8 0 0 12

4 1 0 8

10 3 0 17

5 4 O 13

2 2 1 8

34 11 1 70

Population x 106 Live births x 10 a

3.87 67.7

3.89 64.6

3.95 64.3

3.97 61.2

Cases recognized premortem 9

3,92 65.6

4.00 59.6

"Number of cases treated at major center (Rikshospital data). All cases recognized underwent operation. No other treated cases were found in a survey of other centers in Norway. t Numbers in parentheses represent patients who died. :~Number of cases reported in neonatal death survey. Postoperative deaths from the Rikshospital were reported to the Central Statistical Office and must therefore be subtracted from the number of neonatal deaths in calculating the total cases recognized. In 1971, one patient died of unrelated causes 4 mo after operation and would not appear in the registry, making the total number of cases eight rather than seven, and the 6-yr total 70 rather than 69.

might have been salvaged by earlier recognition and treatment, it seems likely most died soon after birth with CDH of the severe type. Although only 10 of 33 operated infants died, a "visible" mortality of 30%, 46 of the total recognized 70 cases died, for a "true" mortality of 66% (Table 2). The difference between the "visible" or operative mortality of 30% and the " t r u e " mortality of 66% is the "hidden mortality" we wish to emphasize in this communication. Analysis of 33 cases of CDH recognized premortem and operated at the Rikshospital is presented in Table 3. The mortality of those having emergency operations during the first week of life is high, "confirming the experience of others. 1-3 The proportion of right-sided posterolateral hernias in this series is higher than usually reported, 2'4 and the mortality in this group is high. Six of 11 infants with right-sided and only three of 19 with left-sided hernias died.

Autopsy Material The main pathologic finding was the considerable reduction of lung weight in all cases, especially of the ipsilateral lung. Figure 1 illustrates the degree of pulmonary hypoplasia in 15 infants dying before 48 hr of age by comparing lung weights with the expected normal lung weights of infants of similar birth weight? In one extreme case, the ipsilateral lung weighed 3 g and the contralateral lung 10 g when the expected combined lung weight was more than 60 g. Perivascular hemorrhages and interstitial air and blood as evidence of severe mechanical trauma were consistently seen in cases ventilated with high airway pressures, The second striking finding was the paucity of associated life-threatening anOmalies. One patient had multiple anomalies (omphalocele, aplasia of the right diaphragm and right side of the pericardium, and Pierre Robin syndrome).

Table 2. Congenital Diaphragmatic Hernia in Norway (1969-1975) Visible*

True*

Incidence 1.4 cases/yr/million population 1 case/11,605 live births

2.9 cases/yr/million population 1 case/S,455 live births

Mortality 10 died/33 operated = 30.3%

46 died/70 total recognized = 65.7%

"Hidden M o r t a l i t y " - - 3 7 of 70 cases of CDH (52.9%) died untreated 9"Visible" incidence and mortality are calculated on the number of cases seen at a large referral center (Rikshospital). "True" incidence and mortality are calculated on the total number of cases recognized retrospectively including cases diagnosed postmortem (from a survey of neonatal deaths in Norway). "True" incidence and mortality are reliable minimum estimates for reasons given in the text.

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CONGENITAL DIAPHRAGMATIC HERNIA

Table 3. Congenital t)iaphragmatic Hernia Rikshospital ( 1 9 6 9 - 1 9 7 5 ) Age at Operation < 24 Hr

Posterolateral (Bochdalek) Right Left Total Morgagni Eventration

4 (3)*t 14 (3) 18 (6)

1-7 Days

1-65 Wk

Total

4 (3) 3 (0) 7 (3)

3 (0) 2 (0) 5 (0} 2 (1)~ 1 (0)

1 1 (6) 19 (3) 30 (9) 2 (1) 1 (0)

* Numbers in parentheses represent patients who died. t One infant with aplasia of the right diaphragm and right side of the pericardium, omphalocele, and Pierre Robin syndrome; the only infant with an associated life-threatening anomaly. Died of unrelated causes 4 mo after operation.

Another had a patent foramen ovale. Thus, CDH was an isolated anatomic defect in 13 of 15 otherwise normal infants who died, and in all 23 children who survived operation.

Norway only because reliable data were uniquely available. It seems likely that similar numbers of infants with CDH die unrecognized in other parts of the world, but the data base is insufficient to document this neonatal wastage. This report provides reliable minimum estimates of the incidence of CDH in a well-defined population with a well-documented birth rate. The incidence may be considerably greater in a survey in which autopsies are performed on all stillborns and neonatal deaths. Ravitch 6 has pointed out the difficulties of estimating the incidence of such anomalies, the reported incidence of CDH ranging from 1/12,000 to 1/1000 births. Although incidence figures derived by different methods from inherently inadequate data are not strictly comparable, the minimum incidence reported here, 1/5455 live births, is in close agreement with that estimated by Ravitcb ~ (1/4776 live births) from several sources, and that reported by Touloukian 7 (1/4924 live births) from a survey of infant deaths in Connecticut. A high frequency of CDH associated with other life-threatening anomalies has been reported for stillbirths, rais-

DISCUSSION

This report documents an alarming discrepancy between the number of infants with CDH treated at a major referral center and the number of infants who died with CDH as reported in a survey of neonatal deaths during the same 6-yr period. More than half (37 of 70) of the cases of CDH identified retrospectively in Norway from 1969 to 1975 died untreated. These infants died soon after birth and did not come to the attention of a major referral center. There is thus an obvious discrepancy between the "visible" mortality of CDH based on the cases recognized clinically at a major referral center and the "true" mortality based on all the cases identified retrospectively including those reported in a survey of neonatal deaths. This is the "hidden mortality" of CDH. It is unlikely that this "hidden mortality" is peculiar to Norway; it was documented in

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Congenital diaphragmatic hernia: the hidden mortality.

Congenital Diaphragmatic Hernia: The Hidden Mortality By Michael R. Harrison, Roald I. Bjordal, FrCydis Langmark, and O. Knutrud 9 From 1969 to 1975,...
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