Sigmoid colon

The sigmoid colon is the final segment of the descending colon before the rectum, characterized by a curved or S-shaped loop. It is clearly visible in humans and in some species like ruminants but quasi not depictable in carnivores.

Species Differences

• Ruminants (cattle, sheep, goats): The sigmoid colon is typically present and may be palpable per rectum. It lies near the pelvic inlet and serves as a conduit between the descending colon and the rectum.

• Pigs: The sigmoid colon is notably curved and more prominent than in many other species.

• Horses: Although the descending colon is long and can be coiled, a distinct sigmoid portion is not prominent or functionally separated.

• Carnivores (dogs and cats): The colon is relatively short and typically lacks a clearly defined sigmoid section.

Function

• Stores fecal matter before evacuation.

• Absorbs residual water and electrolytes.

• Regulates the timing of fecal transport into the rectum via peristalsis and segmental contractions.

Clinical Importance

• May be involved in colonic impactions or torsions, especially in large animals.

• Accessible during rectal examination, allowing assessment for masses, distension, or displacemen