13th September 2013, Volume 126 Number 1382

Shaw Hua Kueh, Lifeng Zhou, Russell S Walmsley

As of 2007 the waiting time for non-urgent outpatient colonoscopy in the public hospital system in New Zealand was at least 6 months.1 In an attempt to match the growing demand with the scarce resource, patient selection and triaging endoscopy referrals has become critically important.

Several guidelines have been published to assist clinicians in triaging patients for endoscopy. These include documents outlining the role of colonoscopy in various clinical scenario published by the American Society for Gastrointestinal Endoscopy2 and the web-based interactive set of more didactic guidelines by the European Panel on the Appropriateness of Gastrointestinal Endoscopy.3,4

Use of these guidelines has been shown to significantly improve the diagnostic yield of colonoscopies.5-8 At present, no similar guideline exists in New Zealand.

Colonoscopies performed on patients with iron deficiency anaemia and rectal bleeding symptoms give a relatively ‘high’ diagnostic yield9-14 which improves further in those older than 50 years of age.15 For patients with isolated abdominal pain, however, there is less agreement on whether colonoscopy is indicated. The proportion of patients undergoing colonoscopy who have abdominal pain as their primary indication varies significantly around the world, from 2.9% in New York City12 to 53% in a tertiary referral centre in Kuwait.13

The decision to perform colonoscopy is influenced by a number of factors; one of which is the lack of knowledge of the local disease prevalence in patients presenting with isolated abdominal pain. In a report by Neugut from 3 practices in New York City, colon cancer was found in 4.4% and adenomatous polyps of more than 1cm in 2.7%of cases colonoscoped for isolated abdominal pain.12 In a larger multi-centred prospective Swedish study with a study population mean age of 54.7, 2.4% had colon cancer and 3.1% had polyps of more than 1cm.11 Inflammatory bowel diseases were found in 12.2% and diverticular disease in 18.3%.

To help organise local triage for colonoscopy we set out to evaluate the proportion of the colonoscopies performed in the public health system for patients with isolated abdominal pain and determine the local diagnostic yield in this patient group.


The study population was taken from patients attending colonoscopy at North Shore and Waitakere Hospitals, which provide secondary level public healthcare for 513,000 residences in Waitemata District of Auckland, New Zealand. Referral for endoscopy is open-access. There is no standard referral form or guidelines, and so referrals are graded by the Clinical Leader of Gastroenterology, in accordance to Auckland Regional policy used during the study period, as priority 1 (within 1 week), priority 2 (within 3 month) and priority 3 (within 6 months) or return to the referrer if deemed inappropriate.

Registration of all the endoscopies performed at the 2 hospitals was mandatorily and endoscopies were reported on EndoscribeTM database (Mediboss PTY LTD, Bedford Park, South Australia, distributed by Health Communication Network Limited). The following details must be provided before registration was completed and a report of the procedure could be generated: patient’s National Health Index (NHI), name, gender, date of birth, date of the procedure, indication(s), endoscopist(s), procedure(s) performed, findings, biopsy taken and diagnosis.

Patient selection—All colonoscopies recorded in the registry between 1 March 2005 and 28 February 2010 were included in the study. Three groups of patients based on indication for colonoscopy as recorded in EndoscribeTM registry were recruited: abdominal pain, iron deficiency anaemia and overt rectal bleeding.

Patients recruited in the abdominal pain group had to have the colonoscopy performed with the sole indication of abdominal pain. Patients were excluded if they had concurrent indications such as anaemia or rectal bleeding. Similarly, patients with colonoscopy performed for iron deficiency anaemia were recruited into the anaemia group and were excluded if they had concurrent symptoms of rectal bleeding. Other exclusion criteria common to all 3 study groups are listed in Table 1.

The abdominal pain group underwent further screening process by searching the full endoscopic reports from EndoscribeTM and interrogating the ConcertoTM Medical Application (Orion Health Ltd, Auckland, New Zealand).

ConcertoTM allows access to patient details, electronic clinical documentations, hospital admissions and investigations including all blood investigations, tissue histology and radiology reports on all patients in the Greater Auckland area.

Table 1. Inclusion and exclusion criteria


Abdominal pain

Iron deficiency anaemia

Overt rectal bleeding

Group-specific exclusions



Exclusion criteria for all 3 study groups

Altered bowel habit
Weight loss
Abdominal mass
Inflammatory bowel disease
Gastrointestinal surgery
Family history of gastrointestinal malignancy
Incomplete colonoscopies
Therapeutic colonoscopies

Patients were excluded if they were found to have a history of weight loss, altered bowel motion, abdominal mass, family history that warranted surveillance for bowel cancer, history of inflammatory bowel disease, diverticulosis, bowel malignancy or had bowel surgery (except appendectomy and cholecystectomy) which had not been recorded in the EndoscribeTM registry.

Patients with abnormal relevant investigations were also excluded. These include elevated inflammatory makers, anaemia, positive faecal occult blood, raised faecal calprotectin, abnormal barium enema or abdominal Computed Tomography (CT) findings within 6 months prior to colonoscopy.

All histology reports from all study groups were retrieved and reviewed via ConcertoTM. Findings inconsistent with inflammatory bowel disease were categorised as non-specific ulcers or non-specific colitis. Mass lesions were categorised by the most significant abnormality found on histology in descending order of adenocarcinoma, advanced adenomas, non-significant adenomatous polyps and non-significant non-adenomatous polyps.

Advanced adenomas were defined as those with villous or tubulovillous histology, adenoma > 1cm or adenoma with high grade dysplasia. Non-significant non-adenomatous polyps were hyperplastic polyps or metaplastic polyps. Those with polyps reported at colonoscopy but no biopsy taken were presumed to have non-significant non-adenomatous polyps.

Other diagnoses included for analysis (which may occur concurrently) were diverticulosis and haemorrhoids. Diagnostic yield was defined as any abnormalities found at colonoscopy regardless of whether it explained patient’s presenting symptoms or not.

Statistical analysis was performed using SAS® v9.1 software (SAS Institute Inc., Cary, North Carolina, USA). Comparisons of categorical variables were undertaken using Chi-squared test, and Wilcoxon rank sum test was employed for continuous variables inappropriate for parametric tests. P-value of < 0.05 was considered to be statistically significant.

Where sample size is sufficient, multiple logistic regression models were used to analyse the odds ratio (OR) of each diagnosis between patient groups after adjusting for age and gender. The study was registered and approved by Waitemata District Health Board (WDHB) Knowledge Centre (Project Code RM0980711538).


From 1 March 2005 to 28 February 2010, a total of 10,052 colonoscopies were performed. Only 2633 complete colonoscopies performed satisfied all our inclusion and exclusion criteria. Abdominal pain accounted for 1.2% of all colonoscopies performed over the 5-year period, 10.3% for iron deficiency anaemia and 14.7% for overt rectal bleeding.

490 subjects were initially eligible for the abdominal pain group from the EndoscribeTMregistry search; however after further screening, only121 satisfied all inclusion and exclusion criteria. Majority of patients were excluded due to other significant concurrent symptoms, abnormal investigations or incomplete colonoscopy.

The patient demographics are shown in Table 2. Patients in the abdominal pain group were generally younger with a median age of 58, while patients in the anaemia group were generally older with a median age of 73. Table 3 gives the diagnostic findings by indication for colonoscopy.

Table 2. Baseline demographics


Indications for colonoscopy

P value

Abdominal pain
n (%)

Iron deficiency anaemia
n (%)

Overt rectal bleeding
n (%)

Total number




Age range




Median age





<50 years old

41 (33.9)

126 (12.2)

360 (24.3)



70 (57.8)

631 (61.2)

683 (46.1)


Table 3. Diagnosis based on indication


Abdominal pain

Iron deficiency anaemia

Overt rectal bleeding


n (%)

n (%)

n (%)


2 (1.7)

120 (11.6)

122 (8.2)


Advanced adenoma
NS – A

2 (1.7)
15 (12.4)
17 (14.1)

63 (6.1)
110 (10.7)
82 (8.0)

119 (8.0)
147 (9.9)
176 (11.9)



0 (0)

6 (0.6)

23 (1.6)


Crohn’s disease

0 (0)

5 (0.5)

11 (0.7)

Ulcerative colitis

0 (0)

1 (0.1)

12 (0.8)

NS colitis

0 (0)

5 (0.5)

37 (2.5)


NS ulcer

0 (0)

9 (0.9)

8 (0.5)



34 (28.1)

392 (38.0)

514 (34.7)



4 (3.3)

64 (6.2)

382 (25.8)


IBD=Inflammatory bowel disease, NS=Non-significant, A=Adenoma, NA=Non-adenoma; NA† Not available due to inadequate sample size for statistical analysis.

The diagnostic yield—The abdominal pain group had the lowest total diagnostic yield at 48.8% (59/121) compared to iron deficiency anaemia group at 65.2% (672/1031) and overt rectal bleeding group at 78.1% (1156/1481), P <0.001. When controlled for age group alone, the abdominal pain group continued to have significantly lower yield: age <50 - abdominal pain 26.8% (11/41), anaemia 27.8% (35/126), overt rectal bleeding 60.6% (218/360), P <0.001; age≥50— abdominal pain 60% (48/80), anaemia 70.4% (637/905), overt bleeding 83.7% (938/1121), P<0.001.

Amongst those age <50, males with abdominal pain had significantly lower diagnostic yield at 21.1% (4/19) compared to those with anaemia at 36.7% (11/30) or overt rectal bleeding at 65.7% (140/213), P<0.0001. In females, anaemia was associated with lower yield at 25% (24/96) compared to abdominal pain at 31.8% (7/22) and overt rectal bleeding 53.1% (78/147), P<0.001.

In those age ≥50, male with abdominal pain continued to have lower diagnostic yield at 71.9% (23/32) and iron deficiency anaemia was equally low at 72.4% (268/370) compared to those with overt rectal bleeding at 85% (P<0.001). Older females with abdominal pain had significantly lower yield at 52.1% (25/48) compared to anaemia at 69% (369/535) and overt rectal bleeding at 82.3% (441/536), P<0.001.

Using the multiple logistic regression model, patients with abdominal pain were 72% less likely to have an abnormal colonoscopy compared to those with overt rectal bleeding (OR 0.28, 95% CI=0.19–0.42). Similarly, patients with iron deficiency anaemia were 57% less likely to have an abnormal colonoscopy compared to those with overt rectal bleeding (OR 0.43, 95% CI=0.35–0.52).

Patients aged <50 years were 75% less likely to have an abnormal colonoscopy compared to those ≥50 years (OR 0.25, 95% CI=0.2–0.31) and female gender was associated with 25% less likely of having an abnormal colonoscopy compared to male (OR 0.75, 95% CI=0.62–0.90).

Significant neoplasia—The rate of significant neoplasia (i.e. malignancy and advanced adenoma) was significantly lower in patients with abdominal pain at 3.3% compared to 17.8% in the iron deficiency anaemia group and 16.3% in the overt rectal bleeding group (P<0.001).

Among younger patients, there was no significant difference in rate of significant neoplasia between the 3 groups (abdominal pain 2.4%, iron deficiency anaemia 0.8%, overt rectal bleeding 4.2%, P=0.175). However in older patients, abdominal pain group had a significantly lower rate at 3.8% compared to iron deficiency anaemia and overt bleeding group, both at 20.1%, P= 0.001.

When controlling for gender alone, both genders of the abdominal pain group had less significant neoplasia compared to the iron deficiency anaemia group which had the highest rate (female, 4.3% vs 16% respectively, P=0.029; male, 2% vs 20.5% respectively, P=0.05).

Among patients age <50, the rates of significant neoplasia were not different between the 3 groups in both gender groups (female - abdominal pain 4.6%, anaemia 1% and overt rectal bleeding 5.4%; male–abdominal pain 0%, anaemia 0%, overt rectal bleeding 3.3%). Chi-squared analysis was unable to be performed due to inadequate number.

In those age ≥50, abdominal pain was associated with the lowest rate of significant neoplasia in both female and male gender groups (female–abdominal pain 4.2%, anaemia 18.7%, overt rectal bleeding 16.6%, P=0.035; male–abdominal pain 3.1%, anaemia 22.2%, overt rectal bleeding 23.4%, P=0.027). Therefore, young females with abdominal pain were less likely to have significant neoplasia (Table 4).

Table 4. Odds Ratio of significant neoplasia according to indication for colonoscopy and patient characteristics using logistic regression model



95% confidence intervals

Abdominal pain versus overt rectal bleeding




Iron deficiency anaemia versus overt rectal bleeding




Age (< 50 years versus ≥ 50 years)




Gender (Female versus male)




Other diagnosis—Polyps of any histological type were found to be significantly more amongst those with abdominal pain and overt rectal bleeding (age<50–abdominal pain 19.5%, overt rectal bleeding 19.7%, iron deficiency anaemia 7.9%, P=0.009; age≥50–abdominal pain 32.5%, overt rectal bleeding 33.1%, iron deficiency anaemia 27.1%, P=0.013). Further subanalysis did not demonstrate significant difference between genders within their respective age groups.

Amongst the 120 colonoscopies for abdominal pain, none were found to have inflammatory bowel disease. This was significantly less than those with iron deficiency anaemia and rectal bleeding (Table 3). Further subanalysis for age did not show any significant difference and further analysis for age and gender was not possible due to small numbers.

Haemorrhoid was more frequent amongst those with overt rectal bleeding than those with iron deficiency anaemia or abdominal pain. This continues to be true on subanalysis controlling for gender and age (male, age<50–abdominal pain 0%, iron deficiency anaemia 23.3%, overt rectal bleeding 34.7%, P=0.005; female, age<50–abdominal pain 4.6%, iron deficiency anaemia 4.1%, overt rectal bleeding 28.6%, P=<0.001; male, age≥50–abdominal pain 9.4%, iron deficiency anaemia 4.9%, overt rectal bleeding 25%, P <0.001; female, age≥50—abdominal pain 0%, iron deficiency anaemia 6.5%, overt rectal bleeding 22.4%, P <0.001).


Isolated abdominal pain accounted for 1.2% of the total number of colonoscopies performed over the 5-year period in our health authority with an open-access referral system. This is lower than the lowest rate previously reported by Neugut et al at 2.9% in New York over a 4-year period.12

One explanation of this small proportion may be due to triaging of referrals. Abdominal pain was generally not taken as sufficient indication for colonoscopy unless all other reasonable modality of investigations had been exhausted. During the study period, endoscopy service at Waitemata District Health Board continued to be under mounting pressure and waiting time for urgent (Priority 1) would be up to 2 months, while Priority 2 would be up to 6 months.

These long waiting times may have resulted in fewer referrals and may explain the smaller number of colonoscopy performed in this patient group. Although no data was held for the rate of rejection for patients referred with abdominal pain, this was estimated to be approximately 10% according to our triaging Clinical Director of Gastroenterology.

Our overall diagnostic yield in patients with isolated abdominal pain was 49%, which was higher than previously reported.11-14,16-18 However, the definition of diagnostic yield varied significantly between studies.

Our findings are similar to a multi-centred Swedish study where 16% of colonoscopies were performed for abdominal pain, of which inflammatory bowel disease, malignancy, polyps, diverticular disease and benign stricture were found in 48.1% of cases.11

Although Al-Shamali et al reported the highest proportion of colonoscopy performed on patients with abdominal pain at 53.6%, the diagnostic yield was only 7%.13 The study population was different to ours; 53% were Kuwaiti nationals and 47% were from other countries including Egypt, Syria, Jordan and Indian subcontinent, with a much younger average age of 39.2 years.

Accounting for significant pathology of inflammatory bowel diseases and significant neoplasia, the diagnostic yield on our patients with abdominal pain was reassuringly low at 3.3% (4/121). This was 80% less than patients referred with anaemia or overt rectal bleeding (18.3% and 17.8% respectively). On further sub-analysis, the rate of significant pathology was only found in 2.4% (1/41) in those younger than 50 years and 3.8% (3/80) in those 50 and older.

The rate of colorectal malignancy in patients with abdominal pain in our study was comparable to those previously reported from other Western countries of 2.8% in Manchester, UK,18 2.3% in Sweden11 and 0.47% in 2 endoscopy units in San Francisco.17 In our study, there were two cases of colorectal cancer found in the abdominal pain group (1.7%).

The full paper clinical records were obtained and reviewed for these cases. The first case was a 44-year-old female who was found to have a palpable abdominal mass by the referring general practitioner which was recorded on the paper referral form for colonoscopy but was unfortunately not recorded in the EndoscribeTM registry and she was therefore included in our study.

The second case was an 81-year-old female found to have a 15mm pedunculated polyp containing adenocarcinoma which was fully excised. The paper referral letter for this patient stated that the faecal occult blood test was positive but since no laboratory result was found on our search she could not be excluded.

Advanced adenomas were found in 2 cases in abdominal pain group and were both older than 50 (1.7%). In a male patient, tubulovillous adenoma with low grade dysplasia was found and in a female, tubulovillous adenoma with high grade dysplasia was found.

Polyps are one of the most common diagnosis reported, however only 2 studies had distinguish those ≤ 1cm from those ≥1cm. In a prospective study of 68 patients with abdominal pain, 3.05% were found to have polyps ≥1cm.11

The histology of these polyps were not reported. In Yee et al’s report, 0.93% of the 644 patients who had undergone colonoscopy for abdominal pain in San Francisco had polyps of ≥1cm and were all found in patients age >50.17

Among patients with abdominal pain in our study, none were found to have inflammatory bowel disease. The strength of our study therefore lies with our strict criteria under which patients with abdominal pain were recruited. Patients 50 years or older accounted for 97% of diverticulosis found in the abdominal pain group and occurred equally between genders. Similarly, for non-significant non-adenomatous polyps, 82.4% were found in older patients with no difference between genders.

The most significant weakness of our study was that the information available on EndoscribeTM was highly dependent on the endoscopist and was therefore subject to endoscopist variability. The indication for colonoscopy registered was dependent on the endoscopist’s assessment as to the main indication for the colonoscopy.

Similarly the final diagnosis was dependent on the endoscopist to complete and concurrent conditions may not be recorded as the endoscopist may consider these to be irrelevant for patient’s presentation.


At our centres, the current triaging system appears to be effective. We have utilised little resources (1.2% of colonoscopy) on patients with isolated abdominal pain in whom we have demonstrated a low rate of significant pathology.

Although the diagnostic yield was 49% in this patient group, significant pathology was only found in 3.3%. This was even lower in patients younger than 50. Therefore in patients with isolated abdominal pain, particularly those younger than 50, colonoscopy should not be considered as first line of investigation.


Patients with abdominal pain with no other associated symptoms or significant medical history and previously normal investigations prior to referral for colonoscopy accounted for 1.2% of total colonoscopies performed at Waitemata District Health Board. Among these patients, bowel cancer was found in 3.3% which was significantly less than those with iron deficiency anaemia or overt rectal bleeding. When segregated by age, among those younger than 50, no difference in bowel cancer was found between those with abdominal pain, iron deficiency anaemia and overt rectal bleeding. Therefore in patients with isolated abdominal pain, particularly those younger than 50, colonoscopy should not be considered as first line of investigation.



Colonoscopy is an overstretched resource and there is no consensus on whether isolated abdominal pain is an appropriate indication for colonoscopy. We evaluated the proportion of patients referred for colonoscopy with isolated abdominal pain and determined the diagnostic yield for this indication.


All patients registered as having a colonoscopy at Waitemata District Health Board on EndoscribeTM reporting database between March 2005 and February 2010 were included. Patients were recruited based on the indication for colonoscopy of: abdominal pain, iron deficiency anaemia or overt rectal bleeding. All investigations and electronic clinical documents for patients with abdominal pain were retrieved and patients with concurrent anaemia, rectal bleeding, weight loss, altered bowel habit, abdominal mass, previous abnormal investigations and history of inflammatory bowel disease or bowel malignancy were excluded. The diagnostic yield between the 3 study groups were compared using Chi-squared test, Wilcoxon rank sum test and multiple logistic regression models.


Total of 10,052 colonoscopies were performed of which only 2,633 fulfilled our inclusion criteria. The abdominal pain group accounted for 1.2% of colonoscopies performed and had the lowest diagnostic yield of 48.8% (P<0.001). Among those with abdominal pain, significant neoplasia was found in 3.3% and was significantly lower than those with iron deficiency anaemia or overt rectal bleeding groups (P<0.001). When segregated by age, the abdominal pain group continued to have significant less neoplasia (3.8%, P=0.001) among those 50 and older but no difference was found among younger patients.


A small proportion of colonoscopy resources are being used to investigate isolated abdominal pain, which is appropriate given the low diagnostic yield of significant pathology, particularly amongst those less than 50 years old.

Author Information

Shaw Hua (Anthony) Kueh, Medical Registrar, Department of Gastroenterology, Waitemata District Health Board, North Shore, Auckland; Lifeng Zhou, Epidemiologist, Planning & Funding, Waitemata District Health Board, North Shore, Auckland; Russell S Walmsley, Gastroenterologist; Department of Gastroenterology, Waitemata District Health Board, North Shore, Auckland—and Clinical Senior Lecturer, Faculty of Medicine, University of Auckland


Gastroenterology Department, North Shore Hospital, Waitemata District Health Board, Planning & Funding, Waitemata District Health Board, New Zealand


Dr Shaw Hua (Anthony) Kueh, Department of Gastroenterology, North Shore Hospital, Private Bag 93-503, Shakespeare Rd, Takapuna, New Zealand. Fax: +64 (0)9 4868988;

Correspondence Email


Competing Interests

None identified.


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