Distal intestinal obstruction syndrome

Overview

Distal Intestinal Obstruction Syndrome (DIOS) is a gastrointestinal complication primarily seen in individuals with cystic fibrosis (CF). It involves a partial or complete blockage of the distal (lower) small intestine, typically the ileum, due to the accumulation of thick, sticky mucus and undigested food. DIOS is similar in presentation to constipation but occurs deeper in the intestinal tract and can cause more significant symptoms. It most commonly affects adolescents and adults with CF, especially those with pancreatic insufficiency.

Causes

DIOS is caused by the abnormal composition and movement of intestinal contents in people with cystic fibrosis. Key contributing factors include:

• Thickened intestinal secretions: Due to defective CFTR (cystic fibrosis transmembrane conductance regulator) protein, leading to dehydration of intestinal mucus.

• Pancreatic insufficiency: A lack of digestive enzymes causes malabsorption, increasing the bulk and stickiness of intestinal contents.

• Dehydration: Common in CF patients and a contributing factor to inspissated (thickened) stool formation.

• Reduced gastrointestinal motility: Slower movement of contents through the intestines allows material to accumulate and harden.

• Previous abdominal surgery or DIOS episodes: These can increase the risk of recurrence.

Symptoms

Symptoms of DIOS may vary depending on whether the obstruction is partial or complete. Common symptoms include:

• Crampy abdominal pain: Often localized in the lower right abdomen.

• Abdominal distension: Bloating and visible swelling of the abdomen.

• Nausea and vomiting: Particularly in complete obstruction.

• Reduced appetite: Due to discomfort and bloating.

• Absence or reduction of bowel movements: Constipation-like symptoms but deeper in the bowel.

• Palpable mass: A firm, sausage-like mass may be felt in the lower right abdomen.

Diagnosis

Diagnosis of DIOS involves clinical evaluation along with imaging studies to distinguish it from constipation, appendicitis, or other intestinal obstructions. Diagnostic steps include:

• Medical history and physical examination: History of cystic fibrosis and symptom pattern are important clues.

• Abdominal X-rays: May show dilated bowel loops and air-fluid levels consistent with obstruction.

• CT scan: More detailed imaging to confirm obstruction and rule out other causes such as volvulus or intussusception.

• Ultrasound: May be used, particularly in pediatric cases, to assess bowel contents and peristalsis.

Treatment

The goal of treatment is to relieve the obstruction, rehydrate the patient, and prevent recurrence. Treatment approaches include:

• Oral rehydration and laxatives: Polyethylene glycol (PEG) is commonly used to soften and mobilize the stool.

• N-acetylcysteine: Sometimes used orally or via enema to break down mucus in the intestines.

• Enemas or rectal irrigation: Used in partial DIOS to facilitate passage of stool.

• Nasogastric decompression: For severe or complete obstructions, a nasogastric tube may be inserted to relieve pressure and vomiting.

• Hospitalization: May be required for intravenous fluids, pain management, and monitoring in moderate to severe cases.

• Surgery: Reserved for complete obstructions that do not respond to medical treatment or if complications such as perforation arise.

Prognosis

With prompt recognition and treatment, most cases of DIOS resolve without long-term consequences. However, recurrence is common, especially in individuals with poor adherence to enzyme therapy or hydration. Preventive strategies such as regular use of stool softeners, adequate fluid intake, and consistent pancreatic enzyme replacement therapy can significantly reduce the risk of future episodes. Long-term outlook depends largely on the overall management of cystic fibrosis and associated complications.