Primary Torsion of Lesser Omentum Presented with Acute Abdomen and Successfully Managed with Laparoscopic Surgery

To the Editor: Omental torsion can be classified as primary or secondary according to etiology and may be localized in the greater or lesser omentum. Primary torsion of the omentum is characterized with the absence of associated intra-abdominal pathology; however, secondary torsion of the omentum can be associated with underlying factors, including cysts, tumors, foci of intra-abdominal inflammation, postsurgical scars, and hernia sac.[1,2] Omental torsion is a relatively rare cause of an acute abdomen, which often needs surgical management. The pathogenesis of omental torsion has not yet been fully established.[1] Since omental torsion presents with various clinical features, such as no symptom, nonspecific abdominal symptoms, and signs of an acute abdomen, it must be distinguished from other causes of acute abdominal pain, such as cholecystitis, diverticulitis, appendicitis, and other intra-abdominal inflammatory conditions.

A 43-year-old female presented with acute abdominal pain for several days. Abdominal pain was constant and localized in the right lower abdomen. She had no nausea or vomiting, and no remarkable past medical history was noted. Her body temperature was 36.9°C, blood pressure 120/80 mmHg, and pulse rate 80 beats/min with normal rhythm. Abdominal examination revealed tenderness in the lower abdomen without guarding but not in the right lower quadrant. Laboratory tests showed leukocytes 9390/mm³, C-reactive protein 4.47 mg/L, and the other results of routine blood test were within normal limit. Routine chest and simple abdomen X-rays were normal. Contrast-enhanced computed tomography (CT) of the abdomen showed focal, ovoid, fatty infiltration between the left hepatic lobe and the lesser gastric curvature, superior to the pancreas, with a concentric distribution of fibrous and fatty folds converging toward the torsion with edema; the vascular pedicle extended caudally and entered an oval-shaped, well-demarcated fat-containing lesion between the transverse colon and second portion of the duodenum; this mass was 5.9 cm × 3.8 cm × 6.7 cm and contained hyperattenuating streaks [Figure 1a–1c]. We established a clinical diagnosis of torsion of the lesser omentum (or infarction), and laparoscopic exploration was performed. Laparoscopy revealed a 6 cm × 7 cm well-encapsulated inflammatory soft structure originating from the lesser omentum with ischemic changes that occupied the right subhepatic area. The twisted omental pedicle was seen immediately below the left hepatic lobe [Figure 1d]. A small abdominal incision 4.0 cm in length was made above the umbilical trocar and the mass was retrieved through this incision without injury to the capsule. Macroscopically, the fragment had a very soft consistency and a hemorrhagic surface. There was no evidence of mass. Microscopy demonstrated necrotic adipose tissue in the center with hemorrhagic components, surrounded by inflammation. Postoperative recovery was uneventful, and the patient was discharged from the hospital on postoperative day 2.

Figure 1.

(a and b) An abdominal transaxial computed tomography scan showed a whirling oval-shaped fatty mass between the left hepatic lobe and lesser gastric curvature (white arrow); and (c) an abdominal coronal computed tomography scan showed an oval-shaped fatty mass containing hyperattenuating streaks (white arrow). (d) Laparoscopy demonstrated a well-encapsulated, inflammatory soft tissue structure originating from the lesser omentum with ischemic changes occupying the right subhepatic area. A twisted omental pedicle was seen immediately below the left hepatic lobe.

Omental torsion is more frequent on the right side than the left side because of the greater length and mobility of the omentum on the right side of the body.[3] Clinical features of omental torsion are nonspecific. Most patients with omental torsion, therefore, present with sudden localized abdominal pain that is enhanced by abdominal movement with signs of tenderness and rebounded tenderness that may be accompanied by nausea, vomiting, and lower-grade fever. Laboratory findings are often normal or show slight elevations in inflammation parameters.[4] Our patient had clinical features, such as sudden right abdominal pain with tenderness and increased C-reactive protein, but she did not have nausea, vomiting, or leukocytosis. The clinical differential diagnosis of acute abdominal pain depends on age and localization of the pain and includes acute pancreatitis, acute appendicitis, cholecystitis, gastroduodenal ulcer, diverticulitis, epiploic appendagitis, and other intra-abdominal inflammatory conditions. Abdominal ultrasound and contrast-enhanced CT scan can be helpful for diagnosis of omental torsion. Ultrasonography can show a solid, localized, noncompressible hyperechoic mass suggestive of inflammed fat;[3] CT of the abdomen can show a characteristic whirling fatty and fibrous mass near a vascular pedicle, a spiral fatty mass with a whirling pattern, or a circumscribed fatty mass with hyperattenuated streaks and a concentric distribution of fibrous folds.[2,3] In this case, CT of the abdomen showed a whirling hyperattenuated streaks originating from the lesser omentum. Although the whirling pattern of omental torsion has been documented in the literature, not all omental torsion cases showed such characteristic findings. The whirling pattern may not be apparent if the axis of rotation is not perpendicular to the transverse scanning plan.[5]

Management of patients with omental torsion is controversial. Some reports have demonstrated that omental torsion can be managed by conservative treatment with good results because it is self-limiting.[1,3] However, surgical management has been recommended as treatment choice to prevent severe complications following conservative treatment, such as sepsis and intra-abdominal abscess formation. Therefore, laparoscopic resection of torted omentum is treatment choice for omental torsion.[4] In our case, laparoscopic omental resection was performed and the patient was discharged from the hospital on postoperative day 2. Omental torsion, especially that of the lesser omentum, is extremely rare; however, it should be considered in differential diagnosis of acute abdomen because it can cause acute surgical abdomen. Abdominal ultrasound and contrast-enhanced CT scan are useful for the diagnosis of omental torsion because they can rule out other causes of acute abdomen. Although surgical management is the treatment of choice for omental torsion and infarction, conservative treatment can be considered in some uncomplicated cases.

Financial support and sponsorship

This study was supported by Konkuk University in 2016.

Conflicts of interest

There are no conflicts of interest.