Mesentery and Omentum: Surgical POV

Physiology of the mesentery and the Omentum

The Greater and lesser omentum originated from dorsal and ventral midline mesenteries of the embryonic gut. The embryonic stomach rotates at 90 degrees to its longitudinal axis, and because of this rotation, the lesser curvature faces to the right, and the greater curvature faces to the left. Most of the embryonic ventral mesentery is going to be reabsorbed. The portion extending from the fissure of ligamentum venosum and porta hepatis to the proximal part of the duodenum and lesser curvature of the stomach is going to persist. It is known as Lesser omentum. 

The Right border of the lesser omentum is a free edge, and this forms the anterior border of the opening into the lesser sac; that opening is known as the Foramen of Winslow. The embryonic dorsal mesogastrium leads to the formation of the greater omentum. It provides the insulating layer for the protection of abdominal viscera.

Jejunum and ileum are supported by peritoneum-covered dorsal mesentery (it contains blood vessels and lymphatics). The posterior line attachment of mesentery extends from DJ(left side of L2), and it extends towards the right iliac fossa(anterior to the right sacroiliac joint)

Omentum contains a high concentration of macrophages, which aid in the removal of foreign material and bacteria. It is densely adherent to intra-peritoneal sites of inflammation, helping to prevent defuse peritonitis. 

Diseases Of the Omentum that require surgery:

1. Omental Cyst

The omental Cyst is of two types: Unilocular/multilocular. It contains serous fluid. It arises from obstruction of omental lymphatic channels. It is lined by lymphatic endothelium. It is most common in children and young adults.

Clinical features of Omental Cyst

• Small cyst: the patient is asymptomatic and is discovered incidentally. 
• Large cyst: the patient has a palpable abdominal mass. 
• Uncomplicated cysts are freely movable, smooth, and non-tender. 

Complications Of Omental Cyst

• Complications are more common in children. 
• It can lead to torsion/infection/rupture.

Diagnosis Of Omental Cyst

• Diagnosis is made by excision and histological examination.
  • X-ray of the abdomen shows soft tissue density in the mid-abdomen. 
  • A contrast study shows displacement of abdominal organs because of the cysts. There is extrinsic compression of the bowel. 
  • An ultrasound and CT will show a fluid-filled complex cystic mass with internal septation. 

Treatment of Omental Cyst

• Local excision by open or laparoscopic surgery. 

2. Omental Torsion And Infarction 

When the greater omentum is axially twisted along its long axis, it can cause infarction and necrosis if not treated on time. 

Types of Omental Torsion  

• Primary omental torsion: no existing causative condition; It involves the right side of the omentum. 
• Secondary omental torsion is associated with hernia, tumor, or adhesion. 

Clinical features of Omental Torsion

• It is more common in males and most commonly seen in the 4^th to 5^th decade age group. 
• Because of ischemia, the patient will have an acute onset of severe abdominal pain.
• It is located on the right side of the abdomen. 

Examination of Omental Torsion

• Localized abdominal tenderness on palpation.
• Guarding   
• Palpable mass

These signs are also considered as signs suggestive of peritonitis.

Diagnosis of Omental Torsion

• CT: omental mass with signs of inflammation.

Treatment of Omental Torsion

• Resection of involved omentum 
• Correction of underlying condition responsible for the torsion

3. Omental Neoplasms

Omental neoplasm is a Primary malignant neoplasm of omentum. It is rare and are usually sarcomas. Omentum is involved by metastatic tumor via transperitoneal spread. 

Omental Grafts and Transportation topic is discussed in detail in the PrepLadder SS Surgery video topic mesentery and omentum. 

Diseases of Mesesntry that require surgery

1. Mesenteric Cyst

The mesenteric cyst is more common in females; the mean age is 45 years. The most common location is the small intestine (60% of cases). In 40% of cases, it is seen in the colon.

Types of mesenteric cyst

• Chylolymphatic (most common type)
• Enterogenous (second most common type)
• Simple/mesothelial 
• Urogenital remnant 
• Dermoid (teratomatous cyst) 

To read about the Difference between Chylolymphatic and Enterogenous cysts, sign up in the PrepLadder app and watch the videos from the SS Surgery curriculum. 

Clinical features  of Mesenteric Cyst

• Painless abdominal swelling
• Recurrent abdominal pain with or without vomiting 
• Acute abdominal pain due to torsion, rupture, hemorrhage, or infection. 
• Tillaux sign is the swelling moving perpendicular to the attachment of the mesentery .

Tillaux triad

• Soft, fluctuant swelling near the umbilicus 
• Moving perpendicular to attachment of mesentery 
• Zone of resonance around the cyst

Diagnosis of Omental Torsion

• IOC: CECT
• Ultrasound is helpful for diagnosis 

Treatment of Omental Torsion

• Chylolymphatic cyst: Enucleation 
• Enterogenous cyst: Resection + anastomosis 
• Very large cyst: Internal drainage into the peritoneal cavity
• Aspiration alone: It has a high risk of cyst recurrence

2. Acute Mesenteric Lymphadenitis 

In acute mesenteric lymphadenitis, there is Acute right lower quadrant abdominal pain and mesenteric lymph node enlargement. However, the Appendix is normal. It is most commonly seen in children and young adults, and it is equally common in males and females. The organism associated is Yersinia Enterocolitica.

Clinical features of Acute Mesenteric Lymphadenitis

• Acute onset of periumbilical pain
• Shifts to the right lower quadrant over time 
• Nausea/vomiting 
• Diarrhea 
• Anorexia 
• Fever 
• Leucocytosis 

Examination  of Acute Mesenteric Lymphadenitis

• Right lower quadrant tenderness 
• Rebound tenderness 
• Abdominal wall rigidity 

Diagnosis  of Acute Mesenteric Lymphadenitis

The investigation of Choice is Ultrasound 

Treatment of Acute Mesenteric Lymphadenitis

It is a self-limiting disease. If a definitive diagnosis is made with ultrasound, unnecessary surgical intervention can be avoided. 

3. Sclerosing mesenteritis

It is a rare inflammatory disease of mesentery which is characterized histologically on the basis of

• Sclerosing fibrosis 
• Fat necrosis with lipid-laden macrophages 
• Chronic inflammation with germinal centers 
• Focal calcification 

Clinical features of Sclerosing mesenteritis

• Usually seen in the 4^th to 5^th decade
• More common in males
• Most patients are asymptomatic 
• Patients can present with small bowel obstruction 
• Abdominal mass is palpable in more than 50% of patients 

Diagnosis of Sclerosing mesenteritis

• CT findings
  • Fatty mass arising from the base of mesentery; this is called tumoral pseudo capsule  
  • Normal adipose tissue surrounding mesenteric vessels; this is known as the fat ring sign.
  • Normal mesenteric vessels coursing through fatty mass without evidence of vascular involvement or deviation.
  • Intra-abdominal mass displacing adjacent bowel loops without invading them

Definitive diagnosis of Sclerosing mesenteritis

Laparotomy or laparoscopy should be done with a biopsy of the involved mesentery.

Management of Sclerosing mesenteritis

• Spontaneous resolution of symptoms occurs in the majority of patients
• Corticosteroids
• Anti-inflammatory agents Improve symptoms and radiological findings
• Immunosuppressants

Indications of surgery in Sclerosing mesenteritis

• Diagnostic confusion 
• Treatment of intestinal obstruction 

4. Malignant Neoplasms Of Mesentery

The most common neoplasm affecting mesentery is metastasis.. This metastasis results from: 

• Direct invasion of the primary tumor
• Lymphatic metastasis into mesentery 
• Transperitoneal spread of malignant neoplasm into mesentery 

5. Mesenteric and  intra-abdominal desmoid Tumor

The most common primary malignant tumor of the mesentery is the desmoid tumor. This sporadic tumor occurs due to a mutation of the CTNNB-1 gene. 

Management of Mesenteric and  intra-abdominal desmoid Tumor

• Watchful waiting is preferred in patients with stable intra-abdominal desmoid 
• Systemic therapy
  • Slow-growing lesions: Tamoxifen + NSAIDS 
  • Lesions with aggressive behavior: Cytotoxic chemotherapy 
• 10-year survival for intra-abdominal dermoid: 60% to 70%

Also Read: Gastric Lesions : Gastric Bezoar

Frequently Asked Questions

Q: What is the management of slow-growing lesions in the intra-abdominal desmoid tumor?

Answer: Tamoxifen and NSAIDS

Q: What is the management of lesions with aggressive behavior in the intra-abdominal desmoid tumor?

Answer: Cytotoxic Chemotherapy

Question: What are the components of Tillaux?

Answer: The following are the components of Tillaux triad:

• Soft, fluctuant swelling near the umbilicus 
• Moving perpendicular to attachment of mesentery 
• Zone of resonance around the cyst

Hope you found this blog helpful for your GIT, Hepatobiliary and Pancreatic Surgery preparation. For more informative and interesting posts like these, keep reading PrepLadder’s blogs.