Oral water soluble contrast for cancer-related bowel obstruction

Background

Intra-abdominal cancer is where the cancer has either started elsewhere in the body and spread into the stomach area or started in the bowel itself. It can commonly grow and block the movement of food or faeces through the bowel. A blockage of the bowel caused by cancer is known as malignant bowel obstruction (MBO). Some patients with MBO benefit from surgery to reverse the blockage. In others it is not possible to reverse the MBO and it either resolves or becomes permanent (limiting prognosis to days or weeks).

Scar tissue around the bowel (called adhesions) can also cause a blockage, this is known as adhesive small bowel obstruction. Adhesive obstructions often resolve with conservative management in hospital (allowing the bowel to "rest" and recover). However in some, the obstruction requires surgery to remove the scar tissue and fix the blockage.

Oral water soluble contrast (OWSC) is often prepared in liquid form and when swallowed before an x-ray or computed tomography (CT) scan will show up clearly in the bowel. It can predict which people with adhesive small bowel obstruction will require surgery. In some patients it may also speed recovery leading to reduced hospital stay.

It is not clear whether the benefits of OWSC in adhesive small bowel obstruction are also seen in MBO.

Study characteristics

We searched for evidence that OWSC could be used to identify which patients with inoperable MBO would recover with conservative management. We also wanted to know if OWSC increased the likelihood of recovery from MBO, reduced hospital stay or improved prognosis. Finally, we wished to know what side effects OWSC might cause for patients with MBO. We conducted the search in June 2017 and found one study. It only recruited nine participants and did not fully report on the outcomes of using OWSC in MBO.

Key Findings

We found insufficient evidence that OWSC can identify which patients with MBO will recover with conservative management. We found insufficient evidence that patients with MBO benefit from OWSC in terms of length of hospital stay, recovery time or survival. No conclusions could be made about side effects from OWSC.

Quality of Evidence

We rated the quality of the evidence from studies using four levels: very low, low, moderate, or high. Very low-quality evidence means that we are very uncertain about the results. High-quality evidence means that we are very confident in the results. We rated the quality of the evidence as very low due to the lack of studies reporting on the benefits of using OWSC in MBO and the only study we found reporting on side effects recruited very few participants (nine). The low quality of the evidence means that we are very uncertain about the use of OWSC in the management of MBO and cannot confirm its benefits or harms in patients with this condition.

Authors' conclusions: 

There is insufficient evidence from RCTs to determine the place of OWSC in predicting which patients with inoperable MBO will respond with conservative treatment alone. There is also insufficient evidence from RCTs to determine the therapeutic effects and safety of OWSC in patients with malignant small bowel obstruction.

Read the full abstract...
Background: 

Malignant bowel obstruction (MBO) is a common problem in patients with intra-abdominal cancer. Oral water soluble contrast (OWSC) has been shown to be useful in the management of adhesive small bowel obstruction in identifying patients who will recover with conservative management alone and also in reducing the length of hospital stay. It is not clear whether the benefits of OWSC in adhesive small bowel obstruction are also seen in patients with MBO.

Objectives: 

To determine the reliability of OWSC media and follow-up abdominal radiographs in predicting the success of conservative treatment in resolving inoperable MBO with conservative management.

To determine the efficacy and safety of OWSC media in reducing the duration of obstruction and reducing hospital stay in people with MBO.

Search strategy: 

We identified studies from searching Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and MEDLINE in Process, Embase, CINAHL, Science Citation Index (Web of Science) and Conference Proceedings Citation Index - Science (Web of Science). We also searched registries of clinical trials and the CareSearch Grey Literature database. The date of the search was the 6 June 2017.

Selection criteria: 

Randomised controlled trials (RCTs), or prospective controlled studies, that evaluated the diagnostic potential of OWSC in predicting which malignant bowel obstructions will resolve with conservative treatment.

RCTs, or prospective controlled studies, that assessed the therapeutic potential of OWSC in managing MBO at any level compared with placebo, no intervention or usual treatment or supportive care.

Data collection and analysis: 

We used standard methodological procedures expected by Cochrane. We assessed risk of bias and assessed the evidence using GRADE and created a 'Summary of findings' table.

Main results: 

We found only one RCT meeting the selection criteria for the second objective (therapeutic potential) of this review. This study recruited nine participants. It compared the use of gastrografin versus placebo in adult patients with MBO with no indication for further intervention (surgery, endoscopy) apart from standardised conservative management.

The overall risk of bias for the study was high due to issues with low numbers of participants, selective reporting of outcomes and a high attrition rate for the intervention arm.

Primary outcomes

The included trial was a pilot study whose primary outcome was to test the feasibility for a large study. The authors reported specifically on the number of patients screened, the number recruited and reasons for exclusion; this was not the focus of our review.

Due to the low number of participants, the authors of the study decided not to report on our primary outcome of assessing the ability of OWSC to predict the likelihood of malignant small bowel obstruction resolving with conservative treatment alone (diagnostic effect). It also did not report on our primary outcome of rate of resolution of MBO in patients receiving OWSC compared with those not receiving it (therapeutic effect).

The study reported that no issues regarding safety or tolerability of either gastrografin or placebo were identified. The overall quality of the evidence for the incidence of adverse events with OWSC was very low, downgraded twice for serious limitations to study quality (high risk of selective reporting and attrition bias) and downgraded once for imprecision (sparse data).

Secondary outcomes

The study planned to report on this review’s secondary outcome measures of length of hospital stay and time from administration of OWSC to resolution of MBO. However the authors of the study decided not to do so due to the low numbers of patients recruited. The study did not report on our secondary outcome measure of survival times from onset of inoperable MBO until death.

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