347N. Kato et al.: Paraesophageal HerniaSurg TodayJpn J Surg (1999) 29:347–350

Intrathoracic Omental Herniation Through the Esophageal Hiatus:Report of a Case

Naoto Kato, Hiroyuki Iwasaki, Yasushi Rino, Toshio Imada, Tomishige Amano, and Jiro Kondo

First Department of Surgery, Yokohama City University, School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama 236, Japan

Abstract: We report herein an extremely rare case of intratho-racic omental herniation through the esophageal hiatus. Infact, according to our review of the literature, only eight othercases have been reported, most of which were misdiagnosed asmediastinal lipoma after being identified as an intrathoracicmass. We report herein the ninth case of intrathoracic omentalherniation through the esophageal hiatus. A 54-year-oldobese woman was admitted to our hospital for investigation ofa chest roentgenographic abnormality. She was asymptomatic,and her physical examination and laboratory data were allwithin normal limits. Her chest X-ray demonstrated a large,sharply-defined mass, and a computed tomography scan of thethorax indicated a large mediastinal mass with fat density. Athoracotomy was performed under the diagnosis of a medias-tinal lipoma which revealed an encapsulated fatty mass, 10 37.5 3 6 cm in size, that proved to be an omental herniationthrough the esophageal hiatus. There was no herniation of thestomach or intestines into the thorax. The esophageal hiatuswas repaired after the omental mass and hernia sac had beenresected. This case report serves to demonstrate that when-ever a mass of fat density is recognized in the lower thorax, anomental herniation should be borne in mind as a possibledifferential diagnosis.

Key Words: omental herniation, paraesophageal hernia,mediastinum, lipoma

Introduction

The omentum sometimes herniates through congenitaldefects of the diaphragm, such as the foramina ofMorgani or Bochdalek; however, a herniation of theomentum through the esophageal hiatus is extremely

Reprint requests to: N. Kato(Received for publication on Dec. 8, 1997; accepted on July 7,1998)

uncommon. A paraesophageal hiatal hernia in whichthe hernia sac contains the omentum mimics a medias-tinal lipoma,1,2 and a misdiagnosis is thus frequentlymade preoperatively. The following report describes acase of this rare type of hiatal hernia and also tries toidentify some discriminatory features.

Case Report

A 54-year-old obese woman was admitted to our hospi-tal following the discovery of an abnormal shadow onher chest X-ray. The patient was asymptomatic, and herphysical examination and laboratory data were unre-markable. Both a front and lateral view of her X-raydemonstrated a large, sharply defined, and predomi-nantly right-sided posterior mediastinal mass. The massmeasured 8 cm in diameter with a smooth outline, it didnot demonstrate either calcification or cavitation, and itextended inferiorly from the carina to the diaphragmlevel (Fig. 1a,b). A computed tomography (CT) exami-nation of the thorax showed the presence of a mass inthe lower thorax, located on the right side of theesophagus and descending aorta, behind the heart, andbeside the thoracic vertebrae (Fig. 2a). It was bilobularin shape and had biform CT attenuation valves in the2116 and 2134 Hounsfield unit range, which were fatdensities. The line of demarcation was stretched fromthe anterior to the posterior part of the mass. Fine-branching linear strands were present in the mass. Anexamination of the upper gastrointestinal tract revealednormal findings except for a displacement of theesophagus to the left at the level of the mass, probablydue to compression (Fig. 3). There was no herniation ofthe stomach or intestines into the thorax. An uppergastroduodenoscopy revealed a compression of theesophageal right wall from the outer body, but no sig-nificant esophageal hiatal hernia. A thracotomy wasperformed under the initial diagnosis of a mediastinal

348 N. Kato et al.: Paraesophageal Hernia

a b

Fig. 1a,b. Chest X-ray revealed a mass, 8 cm in diameter with a smooth outline, without any signs of calcification or cavitation,and extending inferiorly from the carina to the diaphragm level. (arrows)

lipoma, revealing a 10 3 7.5 3 6cm encapsulated fattymass that proved to be an omental herniation enteringthe posterior mediastinum through a small opening inthe right lateral aspect of the esophageal hiatus. Therewas no herniation of the stomach or intestines into thethorax. Both the omental mass and the hernia sac wereresected, after which the esophageal hiatus was repairedand the defect closed below the esophagus. Beginningnear the central tendon of the diaphragm, at the ante-rior apex of the hiatus, and progressing posteriorly, themargins of fibromuscular crura were repaired with aseries of 1-0 silk sutures spaced about 1cm apart. Fivesutures were needed to narrow the hiatus so that an

opening only large enough to admit the top of a fingercould pass through it alongside the remaining esopha-gus. The patient had an uneventful postoperative recov-ery without any complications.

Discussion

The omentum frequently herniates through congenitaldefects of the diaphragm, such as the foramina ofMorgani or Bochdalek; however, the herniation ofomentum through the esophageal hiatus has rarely beenreported. In fact, according to our review of the medical

Fig. 2a,b. Computed tomography examination of the thorax.a A mass in the lower thorax, located on the right side ofthe esophagus and descending aorta, behind the heart, and

beside the thoracic vertebrae, was demonstrated. b The massappeared to extend continuously through the esophagealhiatus into the abdomen

a b

349N. Kato et al.: Paraesophageal Hernia

both consist of fat tissue. Both CT and magnetic reso-nance imaging (MRI) are helpful for making a differ-ential diagnosis.4,7,8 The CT features in our patient weresimilar in some respects to previously reported findings.Fine linear densities were recognized in the CT film,which were consistent with omental blood vesselsinside the mass. These strands have been described inother reports and tend to suggest omental herniationrather than lipoma.5,7 In our patient, no midline septumwas clearly defined, although biform CT attenuationvalves in the 2116 and 2134 Hounsfield unit rangewere observed, a feature not previously described.Moreover, the line of demarcation was stretched in asagittal direction inside the mass. Such a mass maybe separated into two portions by the occasionalpresence of accessory slips of nonstriated musclewhich combine the esophagus with the left mainbronchus, trachea, pericardium, or aorta.9 When com-paring the CT findings in our patient with three casesreported in the literature,4,5,7 similar bilobular fattymasses were found at the same location in all four.Conversely, Lee et al.7 only reported the midline sep-tum. When we carefully reviewed the CT findings ofour patient after surgery, the mass appeared to extendcontinuously through the esophageal hiatus into theabdomen (Fig. 2b).

MRI would have enabled us to confirm that the masswas fat tissue and would also have allowed for anaccurate evaluation of extension to both sides of thediaphragm, by employing those images in the coronaland sagittal planes. It is regrettable that a preoperativeMRI examination was not done in our patient.

The characteristic CT features for distinguishing anomental herniation through the esophageal hiatus frommediastinal lipoma include a bilobular, retrocardiacfatty mass with multiple thin, soft tissue strands, biformCT attenuation valves, and extension through the dia-phragm. MRI films in the coronal and sagittal planeswould thus be helpful for identifying whether the fattymass continuously extended through the esophagealhiatus into the abdomen. Therefore, CT and MRI arevery useful modalities for establishing a differentialdiagnosis preoperatively.

Regarding the treatment for omental herniationthrough the esophageal hiatus, we recommend that her-nias be repaired whenever a diagnosis is made, regard-less of whether or not they are asymptomatic. Omentalherniation is believed by many to predispose to thedevelopment of a hiatus hernia,5 and a paraesophagealhernia with an intrathoracic stomach is a potentiallylife-threatening condition because its incarcerationcauses complete obstruction, bleeding, and perfora-tion.10 Because the preoperative diagnosis in our patientwas a mediastinal lipoma, a thoracotomy was per-formed; however, when a definite diagnosis of omental

Fig. 3. Examination of the upper gastrointestinal tractrevealed no abnormalities, except for a displacement of theesophagus to the left at the level of the mass, probably due tocompression

literature, the case described herein is only the ninth tobe documented.1–8

It is generally assumed that the major contributingfactors-predisposing to an omental herniation throughthe esophageal hiatus include aging and obesity. Anomental herniation through the esophageal hiatus rep-resents a herniation of perigastric fat, arising from theabdominal surface of the diaphragm, through thephrenoesophageal membrane.5 This membrane has twolimbs, one of which passes through the esophageal hia-tus, then attaches itself to the esophagus in the chest,while the other limb extends downward and attachesitself to the esophagus in the abdomen. The membraneis normally rich in elastic fibers, but in people over theage of 50 years, the amount of elastic tissue decreasesand the esophagus becomes much more mobile withinthe hiatus.7 In obese patients, the omentum may bemore prominent than usual, thus predisposing it toherniation without any significant gastroesophagealhernia.

Omental herniation through the esophageal hiatus ismost likely to be preoperatively diagnosed as intra-thoracic lipoma, due to the fact that the contents of

350 N. Kato et al.: Paraesophageal Hernia

herniation through the esophageal hiatus is made, anabdominal approach is preferable, as it allows forminimal operative intervention and easy repair of theesophageal hiatus. The indication for a laparoscopicoperation should thus be carefully considered for thisdisorder.

Many of the diaphragmatic defects through whichthese hernias take place are impressively large, there-fore it is not surprising that high recurrence rates havebeen reported.11 Although the recurrence of an omentalherniation through the esophageal hiatus has neverbeen reported, these patients must be carefully ob-served postoperatively.

References

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2. Webb WR (1983) Computed tomography of the chest wall,axillary space, pleura and diaphragm. In: Moss AA, Gamsu G,

Genant HS (eds) Computed tomography of the body. Saunders,Philadelphia, pp 383–399

3. Pomerantz RM, Twigg HL (1966) Inthorathoracic omentalherniation. J Thorac Cardiovasc Surg 52:735–736

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10. Menguy R (1988) Surgical management of large paraesophagealhernia with complete intrathoracic stomach. World J Surg 12:415–422

11. Ellis FH Jr, Crozier RE, Shea JA (1986) Paraesophageal hiatushernia. Arch Surg 121:416