Postoperative ileus due to surgical handling: This is the most common cause of postoperative ileus, resulting from the manipulation of the intestines during surgery, which can lead to a temporary cessation of the normal contractions of the bowel muscles.

Opioid-induced ileus: Opioids are commonly used for pain management postoperatively and are known to slow down bowel motility, leading to ileus.
Hypomobility due to anesthesia: Residual effects of anesthesia can affect bowel motility, contributing to ileus.
Fluid and electrolyte imbalance: Postoperative fluid shifts and electrolyte imbalances, particularly hypokalemia and hypomagnesemia, can impair bowel function.
Intra-abdominal infection or abscess: Postoperative infections can cause ileus by irritating the peritoneum and affecting bowel motility.

Mesenteric ischemia: Although less common, this condition can be life-threatening and requires prompt diagnosis and treatment. It involves insufficient blood flow to the intestines, which can occur postoperatively due to various reasons such as embolism, thrombosis, or venous thrombosis.
Internal hernia: Postoperative internal hernias can cause bowel obstruction and ileus, and their diagnosis can be challenging.
Bowel obstruction: Mechanical obstruction of the bowel can cause ileus and needs to be differentiated from a functional ileus.

Porphyria: A group of disorders that can result in acute intermittent porphyria, which may cause abdominal pain, ileus, and neurological symptoms.
Systemic lupus erythematosus (SLE) flare: Although rare, an SLE flare can cause ileus among other systemic symptoms.
Amyloidosis: Involvement of the gastrointestinal tract by amyloid deposits can lead to ileus, among other symptoms, in patients with systemic amyloidosis.