DIOS can be categorised broadly into two categories: incomplete and complete. DIOS typically occurs at the distal end of the small intestine (terminal ileum) and at the start of the large intestine (caecum). This is the narrowest part of the intestines and the site most prone to obstruction.

In DIOS, obstruction of accumulation of thick faecal material occurs either partially (incomplete DIOS) or entirely (complete DIOS). This mass is often difficult to remove as it contains sticky mucoid intestinal content which can adhere the mass to the intestinal wall.

DIOS is a complication unique to cystic fibrosis and has been documented across all age groups. Its incidence increases with age, with 80% of first episodes occurring in adulthood. In the past five years, the reported incidence among individuals over 16 years old has ranged from 4.5% to 7.7%.

DIOS can occur due to several different factors, including the fundamental cause of CF itself; a defective Cystic Fibrosis Transmembrane conductance Regulator (CFTR). A defective form of this protein channel leads to reduced chloride movement, then in turn this leads to reduced fluid secretion into the gut lumen. Additionally, defective CFTR function impacts the epithelial sodium channel (ENaC) which is responsible for the absorption of sodium and water. This leads to further dehydration of the luminal mucus.

Impaired motility can also play a role in DIOS, as patients with CF typically have prolonged gut transit and thickening of intestinal walls.

DIOS can occur in pancreatic sufficient patients but is much more likely to be seen in patients with pancreatic insufficiency (over 90% of cases). If enzyme supplementation is not optimised, this leads to poor absorption of fat, which increases the viscosity of contents in the lumen and activates the ileal brake- the primary inhibitory feedback mechanism which slows gut motility.

There are several risk factors in a CF patient which may contribute to an occurrence of DIOS:

• Certain genotypes associated with severe phenotypes

• Pancreatic insufficiency

• Previous history of meconium ileus at birth

• Previous history of DIOS

• Poorly controlled fat malabsorption

• Dehydration

• Inadequate salt intake

• Medication, e.g., opioids

• Post organ transplantation (due to dehydration, immobility, poor oral intake, drug therapy and post-operative adynamic ileus)

• CF diabetes

• CF liver disease

• Recent change in diet

Symptoms of DIOS usually have an acute onset of days rather than weeks. Type and severity of symptoms are variable in presentation. In general symptoms present as the following:

• Abdominal pain- right lower quadrant, colicky, often intermittent in incomplete and worsening in complete DIOS.

• Nausea and vomiting (often bilious)

• Palpable mass in right lower quadrant of abdomen

• Abdominal distension (more likely in complete DIOS)

• Abdominal tenderness on examination

• Distension

• Feeling of fullness

• Changes in bowel movements (including reduced bowel movements with or without diarrhoea- overflow)

• Obstipation (a severe form of constipation where the person cannot pass stool or gas)

• Take a past medical history of the patient and identify any potential risk factors which may lead to DIOS

• Investigate the presenting symptoms and the time of onset, DIOS is associated with an acute onset.

• Examine the patient’s abdomen for signs of a palpable mass in the right lower quadrant and for any tenderness.

  • Note: some patients may have a longstanding palpable mass in the right lower quadrant which does not cause ileus symptoms, therefore this only requires intervention if there are signs of obstruction.

• If complete intestinal obstruction is suspected, ie vomiting, then request a plain AXR. Signs of DIOS include:

  • Dilated bowel loops with or without intestinal fluid levels

  • Faecal accumulation in right lower quadrant

  • Empty distal colon

• Check serum amylase: intestinal obstruction usually leads to raised levels due to increased absorption of amylase from the intestinal lumen.

The main differential diagnosis is constipation, and it is sometimes difficult to identify if it is a case of mild incomplete DIOS or severe constipation. The time of onset of symptoms are usually different, with DIOS being an acute onset and constipation being longstanding. On an AXR, faecal material is usually seen primarily in the right flank in DIOS but is distributed throughout the colon in constipation.

Other differential diagnoses to consider include:

• Appendicitis

• Appendicular abscess

• Mucocele of the appendix

• Intussusception

• Crohn’s disease

• Adhesions

• Volvulus

• Fibrosing colonopathy

• Malignancy

The following medication may exacerbate the symptoms of DIOS and should be reviewed and stopped if appropriate:

• Opioid analgesia, e.g., codeine, morphine

• Stimulant laxatives, e.g., Senna

Other medication known to commonly cause constipation include:

• NSAIDs, e.g., ibuprofen, naproxen

• Iron supplementation, e.g., ferrous sulphate, ferrous fumarate

• Antimuscarinics, e.g., oxybutynin, solifenacin, tolterodine, procyclidine

• Antispasmodics, e.g., hyoscine

For medical interventions, follow the treatment steps per the treatment flowchart.

Ensure the patient is adequately hydrated, preferably using the oral route if possible, or IV if the patient is unable to tolerate oral fluids.

Monitor electrolytes: patient is likely to be dehydrated and vomiting and/or treatment with laxatives will result in an increased loss of electrolytes, in particular sodium, potassium and calcium.

Patients who have had an episode of DIOS are at a high risk of a reoccurrence and this is observed in about 50% of cases. Therefore, it is important to discuss with the patient measures to put in place to try and prevent this.

• Patients should be encouraged to follow the treatment plan and take their laxatives as prescribed. It is recommended to continue an osmotic laxative (e.g., Movicol^®) for at least 6 months after an episode of DIOS.

• Dietitians should be involved to discuss enzyme supplementation if applicable and ensure the correct doses are taken with each meal and snack.

• Hydration is key and patients should drink plenty of fluids throughout the day

• Regular exercise is also an important part of prevention and an achievable activity plan should be made with the patient.

• Colombo, C. et al. (2011) ‘Guidelines for the diagnosis and management of distal intestinal obstruction syndrome in cystic fibrosis patients’, Journal of Cystic Fibrosis, 10(supplement 2), pp. S24-S28. Available at: https://www.cysticfibrosisjournal.com/article/S1569-1993(11)60005-2/pdf (Accessed: 10 March 2025).

• Cystic Fibrosis Trust (2020) Gastrointestinal issues in cystic fibrosis. Available at: https://www.cysticfibrosis.org.uk/sites/default/files/2020-12/Gastrointestinal%20issues%20in%20CF%20Jul%202020.pdf, (Accessed: 10 March 2025).

• Cystic Fibrosis Medicine (no date) Treatment of Distal Intestinal Obstruction Syndrome. Available at: https://cysticfibrosis.online/dios-2/ (Accessed: 10 March 2025).

• Wilkinson, J., et. al. (2021). Distal Intestinal Obstruction Syndrome (DIOS) , adhesional obstruction and severe constipation management in children with cystic fibrosis. Online at: https://www.clinicalguidelines.scot.nhs.uk/nhsggc-guidelines/nhsggc-guidelines/respiratory/distal-intestinal-obstruction-syndrome-dios-adhesional-obstruction-and-severe-constipation-management-in-children-with-cystic-fibrosis/, accessed 15 May 2025.

• UK Cystic Fibrosis Registry 2023 Annual Data Report (2024), Cystic Fibrosis Trust. London

• UK Cystic Fibrosis Registry 2022 Annual Data Report (2023), Cystic Fibrosis Trust. London

• UK Cystic Fibrosis Registry 2021 Annual Data Report (2022), Cystic Fibrosis Trust. London

• UK Cystic Fibrosis Registry 2020 Annual Data Report (2021), Cystic Fibrosis Trust. London

• UK Cystic Fibrosis Registry 2019 Annual Data Report (2020), Cystic Fibrosis Trust. London

This guideline has been registered with the Trust. However, clinical guidelines are guidelines only. The interpretation and application of clinical guidelines will remain the responsibility of the individual clinician. If in doubt, contact a senior colleague or expert. Caution is advised when using guidelines after the review date.
This guideline is for use in Frimley Health NHS Foundation Trust hospitals only. Any use outside this location will not be supported by the Trust and will be at the risk of the individual using it.

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