Constipation implies infrequent stools (<3 per week), usually associated with hard stools. Obstipation implies a complete absence of gas or stool per rectum, which is highly suggestive of a bowel obstruction.

On physical exam, note the vitals (particularly the presence of fever or tachycardia > 100/min which in association with an intestinal obstruction suggest strangulation with bowel ischemia or perforation). Tachypnea is common with LBO as diaphragm excursion is impaired. On abdominal exam, check for irreducible hernias (leading cause of SBO worldwide). In uncomplicated bowel obstruction, tenderness is generally lacking. The abdomen may be distended and tympanitic. A rectal exam must be performed to rule out fecal impaction, rectal neoplasm, or stricture.

SBOs tend to be associated with more pronounced vomiting. In an early SBO, bowel sounds are hyperactive, with “rushes and tinkles” (high-pitched sounds of hyperperistaltic small bowel). Large bowel obstruction is more likely to be associated with more pronounced distention, less or late onset vomiting, and decreased bowel sounds.

Drugs used to treat neurologic (such as Parkinson’s) or psychiatric diseases can affect colonic motility and predispose to chronic constipation, elongation of the sigmoid, and volvulus, as well as colonic pseudo-obstruction.

The patient presents with progressive massive abdominal distention over several days, nausea, and vomiting (similar to an LBO). However, unlike LBO, the classic setting is in someone who is already hospitalized and often in the postoperative setting.

These are the five common causes of abdominal distention: fat (obesity), feces (fecal impaction), fetus (pregnancy), flatus (ileus or obstruction), and fluid (ascites). Flatus and fluid can be distinguished by whether the abdomen is tympanitic (gas) or dull (fluid) to percussion.

In the USA, malignancies (primarily colon cancer) are the most common cause of LBO (more than half of cases), followed by diverticulitis (either acute or chronic with a stricture) and then volvulus.

Left-sided colon (smaller diameter) cancers are more likely to cause LBO, whereas right-sided colon cancers are more likely to present with iron deficiency anemia.

Malrotation is a congenital condition in which the bowel does not reside in its normal anatomic position. As a result, the bowel and its mesentery are not properly fixed/attached and are therefore prone to twisting and becoming obstructed. Provided the bowel and its mesentery do not twist, the malrotation remains asymptomatic. Volvulus is the term used to describe the twisting of the bowel. Volvulus can be a manifestation of malrotation. If the small bowel twists, the term used is midgut volvulus. Volvulus can also occur in the absence of malrotation (i.e., sigmoid volvulus).