95% of hernias present externally. They are manifested by entrapment of small bowel, occasionally the transverse or sigmoid colon, rarely the cecum. Inguinal hernias may be diagnosed on imaging when gas filled bowel is located below the inguinal ligament.
Ventral or incisional
Colonic hernias involve only those sections with a mesentery (transverse, sigmoid, cecum - not ascending or descending). Left inguinal hernias entrap the sigmoid colon. Diaphragmatic hernias tend to entrap the transverse colon.
As mentioned above, radiographs depict gas filled loops of bowel outside the normal peritoneal confines. Barium enema shows double constriction of the bowel lumen. This marks the entrance and exit of the hernia sac.
Other hernias in the abdomen include:
Richters - One wall of bowel enters a hernia orifice.
Spigellian - Bowel projects through the lateral sheath of the rectus abdominus muscle.