Ultrasound scanning in the diagnosis of acute appendicitis in pregnancy

Ultrasound scanning in the diagnosis of acute appendicitis in pregnancy

Report by Robert Williams, Specialist Registrar

Search checked by Jonathan Shaw, Specialist Registrar

Royal Oldham Hospital, Oldham, UK

A short cut review was carried out to establish whether ultrasonography has valuable clinical utility in pregnant women with suspected appendicitis. Ten papers were found using the reported searches, of which three presented the best evidence to answer the clinical question. The author, date and country of publication, patient group studied, study type, relevant outcomes, results and study weaknesses of these best papers are tabulated. It is concluded that while a positive scan might be a useful indicator, a negative scan is not.

Clinical scenario

A 28‐year‐old woman presents to the emergency department with a 4‐hour history of right iliac fossa pain, and an examination suggestive of acute appendicitis. You are aware that an isolated blood count is neither specific nor sensitive in the diagnosis of appendicitis, and the on‐call surgeon suggests that an ultrasound scan may be helpful.

Three‐part question

In [women with possible appendicitis in pregnancy] is [abdominal ultrasonography] good at [ruling in or ruling out appendicular disease]?

Search strategy

The Cochrane Library Issue 1 2007. Appendicitis[MeSH explode all trees] AND Pregnancy [MeSH explode all trees] 0 results. Medline 1950 to February Week 2 2007. Embase 1980 to 2007 Week 08. Using the OVID interface [appendicitis.mp. or exp Appendicitis/] OR [exp Ultrasonography/or ultrasonography.mp. OR ultrasound.mp. OR sonography.mp.] AND [exp Pregnancy/OR exp Pregnancy Complications/OR exp Pregnancy, Abdominal/OR pregnancy.mp.] Limit to English language and Human. Diagnosis Clinical Query filter (specificity)

Outcome

Ten papers were found, of which seven were irrelevant or of insufficient quality for inclusion. The three remaining papers are shown in table 1.

Table 1.

Author, country, date	Patient group	Study type	Outcomes	Key results	Study weaknesses
Lim et al, 1992, Korea	42 pregnant women with clinically suspected appendicitis.	Diagnostic test study	Sensitivity of USS	100%,	Small numbers
					Unclear selection
					Varying trimesters
	Gold standard operative finding (22) or observation for a median of 3 weeks (23)		Specificity of USS	96%,	3 women in third trimester excluded as uterus too large
			Likelihood ratios	Positive 27.0
				Negative 0.060
Barloon et al, 1995, USA	22 pregnant women with clinically suspected acute appendicitis..	Diagnostic test study	Sensitivity of USS	67%,	Those not presenting with ‘classical acute appendicitis' were not scanned
					Small numbers
					Varying trimesters scanned
	Gold standard operative finding or clinical follow up for a mean period of 19 months (6 to 36 months)		Specificity of USS	95%,
			Likelihood ratios	Positive 12.6
				Negative 0.35
Mullins et al, 2001, USA	29 women with suspected appendicitis who had ultrasound scans performed over a 12 year period	Retrospective cohort	Sensitivity of USS	100%	22 indeterminate scans not included in analysis thus reported clinical utility is for 7 scans
	Gold standard operative findings or record review		Specificity of USS	83.3%

Comments

The results of these studies need to be viewed with caution. All suffer from the handicap of small numbers, likely selection biases and the absence of a gold standard. The analysis of the third study is seriously flawed in that indeterminate scans are not included.

Clinical bottom line

A positive USS may be useful in the diagnosis of acute appendicitis during pregnancy. Those patients with a negative scan should be further investigated and observed until the symptoms resolve or an alternative diagnosis is reached.