Peritoneum & Mesentery

General & Anatomy

  • Peritoneum is membrane that covers abdominal cavity and is lined by mesothelium

  • Falciform ligament

    • Separates the right and left subphrenic spaces

    • Connects peritoneum to diaphragm

    • Remnant of ligamentum teres (umbilical vein)

  • Bare area of liver

    • Posterior and right aspect of liver that is not covered by peritoneum

  • Lesser Sac

Free Air

  • Air should rise so if you see free air that is anti-dependent portion can give you clue as to what organ it is from

Peritonitis

  • Infection

  • Hemorrhage

  • Findings

    • Basically thickening and enhancement of the peritoneal lining, use image above to see the lining as when there is fluid it really just looks like a thickened wall of the abscess but will be in the location of the peritoneal wall, not the abdominal wall!

Peritoneal Malignnacy

  • Rare & hard to differentiate from mets

  • Mesothelioma

    • Associated with prior asbestos exposure

    • Dry type

      • Pain with palpabale abdominal masses

    • Wet type

      • Multiple nodules with ascites

    • Mixed type

  • Carcinomatosis (basically mets to peritoneum), most commonly from

    • Ovarian

    • GI

    • Gallbladder

    • Pancreas

Peritoneal Infection

  • May mimic carcinomatosis

  • TB

    • Typically from reactivation than from primary

Encapsulating Peritoneal Sclerosis

  • Fibrocollagenous cocoon like encapsulation of the small bowel

  • Associations

    • TB

    • Dialysis

    • VP shunts

  • Non-specific shit

    • Thickend peritoneum

    • Fixed bowel loops, thickened bowel, bowel obstruction

    • Peritoneal or mural calcifications - key

    • Loculated ascites

Mesentery

  • Double later of peritoneum that surrounds the organs and keeps them in place

  • Internal hernias

    • Associated with rapid weight loss - look for weight loss surgeries and shit

    • Swirling of vessels (more than 360 deg), likely with vessel caliber changes

    • Pinching or odd angulations of the bowel (90 deg angle would be abnormal)

    • Signs of ischemia

  • Tumors

    • Desmoid

      • Does not metastasize and considered benign

      • Locally aggressive and can engulf adjacent shit

      • Must have complete resection in surgery or they will occur

      • In mesentery, retroperitoneum or abdominal wall muscles

      • Associated with FAP

        • NOTE: Desmoid will be negative on PET where as colon cancer mets would be positive

      • Looks like soft tissue mass

    • Carcinoid

      • Calcifications

      • Typically soft tissue density mass

      • Usually a metastatic finding

        • Look for the primary mass —> look at the bowel wall , may be subtle

    • Liposarcoma or other sarcoma

    • Lymphoma

      • Typically with misty mesentery appearance but with fucked up nodes

  • Infection - Abscess

    • Typically from adjacent process (pancreatitis, appendicitis etc.)

  • Misty Mesentery (Hazy appearance of the mesentery)

    • Increased density of the mesentery without displacement of the vessel

    • May have associated nodes

    • Typically in small bowel mesentery

    • Causes

      • Panniculitis

      • Edema

      • Hemorrhage

      • Neoplastic

  • Creeping fat of the mesentery

    • When fat wall of an inflammatory process

    • Most commonly associated with Crohns

  • Mesenteric Adenitis

    • Clustered LN

    • 3+ nodes which are 5 mm or more each and are homogenous

    • No additional cause on imaging (not reactive)

    • Typically in kids and young adults

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