Congenital Eventration of the Diaphragm

COLLECTIVE REVIEW

Congenital Eventration of the Diaphragm Thomas V. Thomas, M.D.

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nomalies of the diaphragm, particularly eventration, are not encountered frequently in clinical practice. A majority of the adult patients with eventration of the diaphragm are asymptomatic, and the diagnosis is usually entertained only during roentgenographic surveys or during investigation for unrelated symptoms. Although this anomaly of part or all of the hemidiaphragm is an uncommon entity, it deserves stress in the literature and consideration in both differential diagnosis and specific therapeutic measures. Patients with significant eventration of the diaphragm, particularly infants and children, may be in acute pulmonary, cardiac, or gastrointestinal distress, and a clear understanding of the diagnosis and management may be lifesaving. Congenital eventration of the diaphragm has been described in the medical literature under titles such as nonparalytic eventration, neurogenic muscular aplasia of the diaphragm, atrophy of the diaphragm, high-rising diaphragm, and membranous diaphragm [12, 19, 28, 3 1, 461. Despite the difference in various concepts, eventration is generally accepted as an abnormally high position of part or all of the diaphragm, usually associated with a marked decrease in muscle fibers and a membranous appearance of the abnormal area [lo, 12, 15, 291. Eventrations of the diaphragm are divided etiologically into two groups: congenital, or nonparalytic, and acquired, or paralytic, types [46].Congenital eventrations are further divided on an anatomical basis as follows: (1) complete (total); (2) partial: and (3) bilateral. Partial eventrations are separable, based on the embryological segments contributing to the formation of the normal diaphragm, into the following types: (1) anterior; (2) posterolateral; and (3) medial. From the Department of Surgery, University of Kansas School of Medicine, and Veterans Administration Hospital, Kansas City, Mo. Address reprint requests to 4801 Linwood Blvd., Kansas City, Mo. 64128.

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Congenital Eventration of Diaplzragm

The clinical picture of congenital and acquired eventration may be similar, and separation is often difficult in the absence of a history of trauma to the phrenic nerve on the affected side. The separation of the eventrated diaphragm from a paraesophageal diaphragmatic hernia is valuable, particularly in asymptomatic patients. HISTORY

Jean Louis Petit [341 in 1774 was the first to recognize this entity during autopsy studies. It was Beclard [7] in 1829, however, who coined the word eventration. Wood [491 in 1916 expounded further on eventration and made a plea that one should not confuse this with diaphragmatic herniations. In 1923 Morrison [31] performed the first successful repair of an eventrated diaphragm and utilized one of the presently applied techniques of plication to remove the redundancy associated with it. Bisgard [I01 in 1947 did the first successful repair of congenital eventration of the diaphragm. He provided the presently accepted definition of eventration as “an abnormally high or elevated position of one leaf of the intact diaphragm as a result of paralysis, aplasia, or atrophy of varying degrees of the muscle fibers. T h e unbroken continuity differentiates it from diaphragmatic hernia.” Bilateral eventrations of the diaphragm in infants and children have been reported by Avnet [4] and others [21, 261. With a greater awareness of this entity, a larger number of these lesions are suspected on plain chest roentgenograms, and specific investigations as well as treatment are institutcd in symptomatic patients. DEVELOPMENT A N D INCIDENCE

Development of the diaphragm and separation of the coelomic cavity into thoracic and abdominal cavities takes place sometime during the eighth to tenth weeks of intrauterine life. T h e septum transversuin arises caudal to the heart and grows dorsally to join the mesentery of the foregut. The pleuroperitoneal membrane arises from the dorsolateral aspect and meets the ventral portion of the septum transversum and medial segment of the mesentery. Defects or failure of fusion of these elements result in herniation of the abdominal contents into the thoracic cavity. Pleuroperitoneal folds of the diaphragm are composed only of reflections of pleura and peritoneum until later in intrauterine life. This layer is thought to be heavily impregnated later by an ingrowth of cervical myotomes between the two membranes. T h e right hemidiaphragm usually closes first. Early in the development of the septum it moves caudally from the cervical region, carrying with it the nerve supply [29, 33, 35, 471. With the normal progression of intrauterine changes, the midgut VOL. 10,

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rotates and returns to the abdominal cavity at about the tenth week of fetal life. A premature return of the viscera to the peritoneal cavity is believed to be a factor in the delay or failure of the diaphragm to develop normally, sometimes resulting in defects or stretched-out portions rising high into the thoracic cavity. These may be associated with the absence of ingrown striated muscles into the septum. Anomalies of the abdomen or a rapid enlargement of the abdominal contents may also be contributing factors. T h e lung may be the victim of compression, hypoplasia, or agenesis on the ipsilateral side. T h e abdominal orgahs may encroach on the pleural space by migration with a mediastinal shift and rotation of the heart. T h e spleen, stomach, colon, kidney, small bowel, liver, and adrenal gland may be found under the highrising portion of the diaphragm. Bony abnormalities of the sternum, ribs, and vertebrae may also be encountered with congenital eventrations [2, 3, 15, 16, 33, 47, 501. T h e peripheral portions of eventrated diaphragm may have usually well-developed muscular elements. T h e involved area of the diaphragm may be sparsely muscularized or converted to a translucent aponeurotic membrane. In an analysis of 2,500 chest roentgenograms on infants, Beck and Motsay [6] found the frequency of eventration to be 4%, but only 3 infants had symptoms attributable to the anomaly. Chin and Lynn [17] in 1956 reviewed 412,000 chest roentgenograms and found only 32 patients with the diagnosis of eventration. Only 5 of their patients were symptomatic enough to require surgical treatment. T h e clinical separation of congenital eventrations is unreliable in adults, and it is often attained by a process of excluding the factors likely to contribute to phrenic nerve paralysis. CLINICAL PICTURE

Many patients with complete eventration of the hemidiaphragm and most patients with partial eventration usually remain asymptomatic; therefore, diagnosis is often an incidental feature. Changes in the compliance of lungs and chest wall, or excessive weight gain, may cause symptoms in a hitherto asymptomatic patient [30, 401. When the patient is symptomatic, there may be little, if any, difference in symptomatology between a large diaphragmatic hernia and eventration. An evaluation of the maternal, obstetric, and pediatric history is helpful in excluding acquired eventrations. Acute respiratory distress and difficulties in feeding are the most pronounced symptoms of eventration in infants [15, 24, 40, 431. These infants may be dusky and occasionally cyanotic. In children there may be evidence of repeated attacks of pneumonitis on the affected side and in some cases bronchitis or bronchiectasis. There may be exaggeration of cardiorespiratory and 182

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Congenital Euentralion of Dinphragnz

gastrointestinal symptoms when the patient lies flat or in a head-down position, or after heavy meals [15, 18, 201. An acute shift of the mediastinum may precipitate cardiac arrhythmias and obstruction to venous re turn. Nonspecific gastrointestinal symptoms, such as lack of appetite, inability to gain weight, epigastric discomfort, heartburn, belching, constipation, and symptoms of intermittent intestinal obstruction, may be seen frequently in children or adults. Pain may be referred to the periumbilical area when there is pulling or stretching of the mesentery or when there are fibrous bands across the intestines and mesentery. Palpitation, tachycardia, and dyspnea at rest or on exertion are frequent complaints of adults [l, 27,291. These symptoms may show characteristic aggravation with changes in posture [15]. In patients with a moderate or severe degree of eventration, a scaphoid-shaped abdomen and fullness in the lower chest on the affected side may be obvious on inspection 12, 3, 81. Uninhibited divergence of the lower intercostal spaces during inspiration was first described as a characteristic finding of eventration by Hoover in 1920 [22]. Dullness on percussion of the lower chest, diminished or absent breath sounds, and the presence of peristaltic sounds high in the chest are other physical findings which could raise the question of eventration of the diaphragm [12, 16, 20, 251. T h e heart and trachea may be shifted to the opposite side with cephalad or contralateral shift of apical pulsation (pseudodextrocardia) [ 151. Increased anteroposterior diameter of the lower chest on the ipsilateral side may be another finding. When there is extreme redundancy of the diaphragm, a flapping sound may be heard during respiration as an additional sign [29]. In most of the patients, physical examination may contribute little to the diagnosis of eventration. DZA GNOSZS

Localized eventrations are almost always asymptomatic, and the diagnosis is usually confirmed only at thoracotomy for unrelated surgical procedures or during autopsy (Fig. 1). Posteroanterior and lateral chest roentgenograms may give conclusive evidence in a majority of cases, but separation from a small diaphragmatic hernia is usually difficult [23]. In symptomatic patients further investigations are superfluous, especially in infants. Barium enema and upper gastrointestinal studies may show a high-rising colon or upside-down stomach with or without volvulus and a thin diaphragmatic outline overlying it (Fig. 2). A necklike area on barium studies is believed to be more indicative of a diaphragmatic hernia. Other contrast-material studies and fluoroscopy should be considered if diagnosis is uncertain, and they may be essential to exclude VOL. 10, NO. 2 , AUGUST,

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B

FIG. 1. Posteroanterior ( A ) and right lateral ( B ) cheJt roentgenograrns of a n asymptomatic patient showing partial euentration of t h e right hemidiaphragm. Comparison with the chest roentgenograms taken 4 , 10, and 12 years earlier on this patient showed no change in the appearance.

lesions such as pulmonary cysts, pericardial cysts, intrathoracic lipomas, duplication cysts, and subphrenic abscesses. On fluoroscopic examination a true paradoxical motion is not present in congenital eventration of the diaphragm. T h e initial passive upward movement of the redundant portion of the diaphragm, until the slack is taken up, is sometimes confused with paradoxical motion [lo, 15, 17, 231. T h e muscularized portions will contract simultaneously with the opposite diaphragm. Bilateral medial segmental eventrations of the diaphragm are often confused with mediastinal tumors; however, on fluoroscopy these areas may show respiratory diaphragmatic movements [4,261. Inversion of the left hemidiaphragm with pleural effusion has been described recently as a new diagnostic problem in diaphragmatic pathology [45]. Duplication and scalloping of the diaphragm occasionally add to the complexity of differential diagnosis [ 151. Scalloping (hypertrophy and contraction of muscle bundles) of the diaphragm may alternate with localized eventrated portions in the diaphragm. Roentgenograms of the chest, with the patient in the lateral decubitus position, are usually helpful in delineating the location of subpulmonic (supradiaphragmatic) accumulation of fluid, which casts the shadow of a high diaphragm. Diagnostic pneumoperitoneography was first introduced by Zeitlin in 1930 [50]and has been widely used since then. Carbon dioxide 184

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Congenital Evetitration of Diaphragm

CheJt ioentgenogianz of a ?S-yeai-oid m a n with minimal s h o i l n e ~of ~ breath, occasional palpitation, and some left upper quadrant discomfort, showiiig rotation of the heart to the right and a markedly elevated left hemidiaphragm. F I G . 2.

or nitrous oxide, 7 to 10 cc. per kilogram of body weight, has been preferred over atmospheric air or oxygen for this study [Zl]. Upright chest roentgenograms after introduction of diagnostic pneumoperitoneum are usually confirmatory and clearly outline the aponeurotic portion of an eventrated diaphragm. Laminagrams may be useful in some instances. Radioisotope photoscanning of the liver alone or in combination with the lungs is also a valuable adjunct to diagnostic procedures [35, 461. A decrease in perfusion in the lower lobes of the affected side has been demonstrated by radioisotope scans and pulmonary angiograms [2, 8, 401. Bronchospirometry of the affected lung has shown a decrease in ventilation of as much as 50 to 70% according to some studies [25,40,48]. This information is valuable for comparison of postoperative results, although lungs with well-developed fibrotic changes are likely to show little or no improvement after repair of eventration. Patients with poor pulmonary function, however, may be expected to have some gain following repair [40]. Bronchoscopy and bronchography may reveal compression of the ipsilateral lower lobe along with deviation and upward displacement of the upper lobe bronchus [18, 25, 311. Although the normal diaphragm may account for as much as 60% of the total ventilatory motion [48], pulmonary compliance is considered to be an important factor [30]. T h e average excursion of the dome is approximately 3.5 cm. [30], which may be diminished due to poor diaphragmatic contraction in eventration. Pulmonary function studies on some patients reported in the literature show an imVOL. 10, NO. 2 , AUGUST,

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provement of as much as 50'); on the affected side [12, 18, 25,40,43,441. If history and preoperative investigations are not helpful in determining the developmental nature of eventration, it may be confirmed by faradic stimulation of the phrenic nerve at the time of thoracotomy [29, 401. T h e technique of recording intragastric pressure during respiratory variations (Schlippe's test) is of little value in the diagnosis of eventration of the diaphragm [39]. PREOPERA TI VE M A N A G E M E N T

Infants with cyanosis or acute respiratory distress may be saved by prompt recognition and institution of specific therapy. Resuscitative measures with a face mask are to be discouraged if a large eventration or diaphragmatic hernia is suspected because of the danger that symptoms may be aggravated by inflating the stomach with air or oxygen [3, 6, 29, 421. Endotracheal intubation with positive-pressure ventilation and sufficient humidity are usually lifesaving measures. A high concentration of oxygen, in addition to relieving cyanosis, helps to minimize the necessity of excessive diaphragmatic excursion. Humidity prevents drying u p of bronchial secretions and reduces the insensible loss of water. Continuous gastric decompression with the use of a nasogastric tube is extremely helpful in removing swallowed air and gastric secretions while minimizing impingement of the stomach on the diaphragmatic motion. T h e patients who are not supported by positive-pressure breathing should be maintained in a semiupright position on the affected side. Since many of these infants are acidotic, it may be necessary to administer sodium bicarbonate prior to operation [S]. Congenital eventrations may remain asymptomatic until later in life when obesity or pulmonary disease becomes involved. Sometimes congenital eventration of the diaphragm is complicated by cardiac, pulmonary, or gastrointestinal anomalies, and it is imperative to recognize the dominant lesion responsible for the symptoms. Necessary parenteral fluids, electrolytes, and vitamins are administered while the patient is being evaluated for surgical correction. Adult patients who have multiple complaints and are in no acute distress should be investigated carefully in order that the surgeon may ascertain the role of the eventrated diaphragm before recommending surgical treatment [27, 29, 461. Although small localized eventrations are asymptomatic, small diaphragmatic hernias are likely to be associated with varying degrees of symptoms and complications. Therefore an attempt should be made to separate the two entities. Preoperative laxatives and enemas are helpful in obtaining an empty bowel and reducing unnecessary tension on the suture lines in the diaphragm. 186

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Congenital Eventration of Diaphragm

SURGICAL REPAIR

My experience has been with a total of 12 symptomatic patients at

three separate institutions. Eight symptomatic patients with congenital eventration, 6 of whom had successful repairs, have been reported earlier [461. No operation was recommended for an infant in the remaining group who had agenesis of the left lung, multiple anomalies, and partial eventration of the right hemidiaphragm. In another case a partial asymptomatic eventration of the left hemidiaphragm was repaired during a thoracotomy for a penetrating wound of the mediastinum. A 78-year-old man (Veterans Administration Hospital, Kansas City, Mo.) with a history of several years of intermittent upper abdominal pain, discomfort, and palpitation was not operated upon because of prompt relief of symptoms with parenteral fluids and nasogastric suction (Fig. 3). I collaborated in repairs done in two other patients, a 68year-old woman (St. Thomas Hospital, Nashville, Tenn.) and a 5-day-old infant (Children’s Hospital, Louisville, Ky.), both of whom have made uneventful recoveries. Recently, an asymptomatic eventration of the entire left hemidiaphragm in a 2 l-year-old primigravida suddenly became symptomatic when the woman reached full-term pregnancy, with

A

B

FIG. 3. ( A ) Postcroantel-ior chest roentgenogram of patient with history suggestive of recurrent large bowel obstrirction occurring mon.ths and years apart and spontaneous remission after several hours. T h e left hemidiaphragm is thin and located high, producing shift of nzediastinal structures. ( B ) Lateral view of the chest of the same patient shows the entire left hemidiaphragm to be a rnern.branot.1~ .rtrzirtnre w i t h gas-filled co.’onic scgmcnts occirpying the lower thoracic region. VOL. 10, NO. 2, AUGUST,

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tachycardia, orthopnea, constipation, and severe, cramping left upper quadrant pain. Roentgenograms of the chest and abdomen were consistent with volvulus of the splenic flexure and transverse colon under the eventrated left hemidiaphragm. Induced labor and forceps delivery corrected the volvulus of the colon and respiratory distress. She is a candidate for elective repair of the eventration before the next pregnancy. T h e consensus of most authors is in favor of a transthoracic approach for repair of the eventration. Adequate mobilization of the diaphragm to the level of the primary attachments is unlikely through the abdominal approach. T h e overhanging costal cartilages and the presence of an easily traumatized spleen considerably limit thorough exploration and mobilization of the diaphragm. T h e thoracic approach also reduces the likelihood of postoperative ileus. Surgical treatment has been strongly advocated and successfully carried out by Bisgard [lo], State [42], Butsch and Leahy [14], Shellito and Bartlett [41], Koop and Johnson [24], Beck and Motsay [6] and others [18, 20, 27, 36, 40, 43, 461 on symptomatic patients. With a better understanding of the physiological changes in eventration and improvements in surgical techniques and anesthesia, as well as subjective and objective evidence of improvement following repair, most authors justify surgical treatment. T h e transthoracic approach is accomplished through a posterolateral thoracotomy with an incision along the fifth, sixth, or sometimes seventh intercostal space, as has been advocated by most authors. When the infants are in acute respiratory distress, an anterolateral thoracotomy with the head end of the table tilted u p may be preferable. T h e diaphragm is carefully mobilized to the level of its primary intercostal attachments. I like to open the membranous portion and free the attachments to the colon, spleen, stomach, or other abdominal viscera, resect the excess membranous portion, and carry out a two-layer overlapping type of approximation with nonabsorbable interrupted sutures [46]. In infants with acute symptoms, this approach has not been used because of the longer operative time and dissection required. Most reports in the literature favor a simple plication of the diaphragm in adults and children to remove the redundancy [lo, 20, 24, 29, 36, 421. Opening the diaphragm provides a valuable but limited exploration of the upper abdomen and avoids inadvertent injury to underlying viscera. T h e abdominal approach is recommended when bilateral eventrations are encountered, since total correction can be accomplished through one incision during the same procedure [21]. Others have utilized two separate thoracotomies a few weeks apart [4,261. Care should be taken to avoid injury to the major ramifications of the phrenic nerve during repair. For better function and results, an attempt is made to bring together the muscularized portions of the diaphragm with good 188

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Congrnital Euenti ation of Dinphi ngrn

contractility. If the medial segment of the diaphragm is inadequate, the pericardium may be reflected and sutured to reinforce the area [46]. Different autogenous tissues, such as fascia lata, portions of the abdominal or chest wall, or synthetic materials have been used by others [37]. Gastric decompression and waterseal drainage of the pleural space are provided in the immediate postoperative period. Enthusiastic attenipts at inflating a hypoplastic or fibrotic lung to fill the dead space are unwarranted and may cause a rupture of the alveoli or emphysematous changes [8]. Pulmonary hypoplasia is a real threat to the survival of newborn infants with corrected eventrations as well as diaphragmatic hernia. Areechon and Reid [ Z ] believe that these small lungs have differentiated to the alveolar phase from the glandular stage and that the number of alveoli found distal to the terminal bronchioles is normal. This may mean that the correction of the deformity will lead to aeration and growth of the hypoplastic lung [Z,81. It is possible in rare instances that with the laxity of the diaphragm corrected and visceral contents returned, the peritoneal cavity will not be a large enough receptacle. T h e creation of a temporary ventral hernia may be necessary, as has been advocated with the correction of a large diaphragmatic hernia, in infants 1241. This may be helpful in avoiding disruption of the repair or obstruction of lymphatic and venous return. Recurrence of the eventration, although rare, may be a factor with inadequate repair or injury to phrenic nerve. In 1954 Bingham [9] reported two cases of eventration following breech delivery. Some of the infants with eventration noted as a complication in obstetric procedures usually got complete relief within days or weeks [28, 381. McNamara and associates [27] have advocated the reconstruction of the cardioesophageal junction to prevent gastroesophageal reflux following repair of eventration. P A T H O L O GY

A majority of the eventrations, particularly the cornplete variety, are located on the left side. Reed and Borden [36], in an analysis of 183 cases, found 165 eventrations to be located on the left side. Men are affected more frequently than wcmen. Butler and Claireaux [ l S ] estimated that diaphragmatic anomalies, such as hernia and eventration, accounted for 1.4% of all Ferinatal deaths. Although several maternal and infantile diseases have been considered to be etiological lactors in eventration of the diaphragm, true nonparalytic or congenital eventration is thought to be a weakness of the diaphragm resulting from a lack of, or inadequate, muscularization. With a history of trauma, inflammatory processes of the respiratory tract and upper abdomen, or neoplastic growths, the acquired type of eventration is more likely. In those cases a true paradoxical motion of the diaphragm is seen on VOL. 10, NO. 2, AUGUST,

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fluoroscopic examination and no response can be elicited upon faradic stimulation of the phrenic nerve [5, 9, 11, 15, 18, 19, 481. In congenital eventration the phrenic nerve may be smaller, but it is intact and will respond to electrical stimulation. T h e term neurogenic muscular aplasia of t h e diaphragm is probably more representative of the abnormalities observed than the common term euentration [12]. T h e diaphragm in these patients is usually a thin, stretched-out, aponeurotic structure with a few scattered muscular fibers. A quantitative deficiency of nerve fibers is also noted in this area [29, 401; however, the edema, hyalinization, or degeneration of nerve fibers and muscles seen in acquired eventrations is lacking. Eventration of the diaphragm has often been compared to a direct defect in the inguinal region, in contradistinction to the comparison of diaphragmatic hernia to an indirect type of hernia with a sac forming the covering. With congenital eventration some authors feel that three separate layers should be visible on microscopical examination. T h e attenuated portion is often made u p only of fibroelastic tissue. N o reports are available to indicate the longterm changes in histological structure of the diaphragm with phrenic paralysis, especially in regard to the possibility that such changes are inseparable from the congenital eventration. SUMMARY

Although abnormal elevation of the diaphragm is seen in only a small percentage of the population, the need for accurate diagnosis and a knowledge of the etiological factors is well known. Surgical therapy may be required in only a small percentage of such patients, but it may be a lifesaving measure in infants and children with respiratory insufficiency. Cardiorespiratory and gastrointestinal symptoms are usually associated with large eventrations of the diaphragm. Surgical repair is recommended for symptomatic patients, and success is achieved with a low morbidity or mortality. T h e results of surgical correction are usually gratifying and often dramatic. This review deals primarily with the congenital variety of eventrations, the clinical picture, diagnosis, treatment, results, and pathological changes of this entity. T h e observations made in this review have been accumulated from reports in the literature as well as from clinical experience with a limited number of patients. ACKNOWLEDGMENT

I would like LO express my appreciation to Herbert T. Ransdell, Jr., M.D., Professor of Surgery, Section of Thoracic Surgery, University of Louisville School of Medicine, Louisville, Ky., for the supervision and encouragement in the suc-

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cessful management of some of the patients which prompted this review antl tlie earlier report. REFERENCES

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THOMAS 25. Larson, R. K., and Evans, B. H. Eventration of the diaphragm. Amer. R e v . Resp. Dis. 87:753, 1963. 26. Lindstrom, C. H., and Allen, R. P. Bilateral congenital eventration of the diaphragm. Amel-. J. Roentgen. 97:216, 1966. 27. McNamara, J. J., Paulson, D. L., Urschel, H. C., and Razzuk, M. A. Eventration of the diaphragm. Surgery 64:1013, 1968. 28. Meylar, L., and Huizinga, E. Temporary high position of the diaphragm. J. Thorac. Surg. 19:283, 1950. 29. Michelson, E. Eventration of the diaphragm. Surgery 49:410, 1961. 30. Milne, E. N. C., and Bass, H. Relationship between specific dynamic pulmonary compliance and diaphragmatic excursion. Radiology 92:615, 1969. 31. Morrison, J. M. W. Elevation of one diaphragm, unilateral phrenic paralysis: A radiological study with special reference to differential diagnosis. Arch. Rndiol. Elrctrother. 27:353, 1923. 32. Nylander, P. E. A., and Elfving, G. Partial eventration of the diaphragm. A n n . Chir. Gynaec. Fenn. 40:1, 1951. 33. Patten, 13. M. H u m a n Embryology (2d ecl.). New York: McGraw-Hill, 1953. P. 505. 34. Petit, J. L. Trait& rlrr Maladies Chirzirgicales rt der Ope'l-ations Qui L f w r Convifvment: Owl-age Posthzime de J. L. Petit (Revised ed.). Lesne, 17'30. Vol. 11, p. 233. 35. Ravitch, M. M., and Handesman, J . C. Defects in right diaphragm of infants and children with herniation of liver. A.M.A. Arch. Surp. 64:794, 1952. 36. Reed, J. A., and Borden, D. L. Eventration of the diaphragm: Arch. Surg. 31:30. 1935. 37. Sanfoid, M. C. Eventration of the diaphragm repaired utilizing tantalum mesh. J . Thoruc. Surg. 31:731, 1956. 38. Schifein, N. Unilateral paralysis of the diaphragm in the newborn infant clue to phrenic nerve injury with and without associated brachial palsy. Pediatrics 9:69, 1952. 39. Schlippe, P. Physikalische Untersuchungen bei der Anwendung des Magenschlauches. Deutsch. Arch. Klin. Med. 76:450, 1903. 40. Shah-Mirany, J., Schmitz, G . L., and Watson, R. R. Eventration of the diaphragm: Physiologic and surgical significance. Arch. Szirg. (Chicago) 96: 844, 1968. 41. Shellito, J. G., and Bartlett, W. C. Surgical correction of congenital eventration of the diaphragm. Amer. Surg. 17:898, 1951. 42. State, D. T h e surgical correction of congenital eventration of the diaphragm in infancy. Surgery 25:461, 1949. 43. Stephenson, R. H., and Hopkins, W. A. Volvulus of the stomach complicating eventration of the diaphragm. Amer. J . Gastroent. 41:225, 1964. 44. Svanberg, L. Clinical value of analysis of lung function in some intrathoracic diseases. Actu Chir. Scand. 111: 169, 1956. 45. Swingle, J. D., Logan, R., and Juhl, J. H. Inversion of the left hemidiaphragm. J.A.M.A. 208:863, 1969. 46. Thomas, T. V. Nonparalytic eventration of the diaphragm. J . Thorac. Cardiovasc. Surg. 55:586, 1968. 47. Wells, L. J. Development of human diaphragm and pleural sacs. Contrib. Embryol. 35:107, 1954. 48. Werner, I. Changes in the respiratory mechanism following phrenicectomy. J.A.M.A. 95:1162, 1930. 49. Wood, H. G. Eventration of the diaphragm. Surg. Gynec. Obstet. 23:344, 1916. 50. Zeitlin, N. S. Diagnostic pneumoperitoneum in diaphragmatic pathology. Radiology 14: 152, 1930.

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