Summary of Common Conditions Seen in OSCEs
| Condition | Key features in history | Key investigations |
| Infective causes | ||
| Bacterial/viral gastroenteritis | Recent takeaway/restaurant Recent barbecue Raw/undercooked meat or seafood, unpasteurised milk Foreign contacts, travel abroad Contacts with diarrhoea | Stool microscopy, culture and sensitivity if suspecting bacterial cause Full blood count and Us+Es (for haemolytic-uraemic syndrome or Escherichia coli) |
| Clostridium difficile | Recent antibiotic use Green, foul-smelling diarrhoea | Clostridium difficile toxin |
| Malignancies | ||
| Bowel cancer | Melaena (tarry black stool) Rectal bleeding Weight loss, loss of appetite | Colonoscopy and biopsy Full blood count + mean corpuscular volume (microcytic anaemia) Ferritin (iron deficiency) |
| Inflammatory | ||
| Inflammatory bowel disease (ulcerative colitis, Crohn’s disease) | Young Blood and mucus in stool Systemic symptoms of IBD:
| Colonoscopy and biopsy Barium studies Erythrocyte sedimentation rate |
| Malabsorption | ||
| Coeliac disease | Steatorrhoea (offensive-smelling ‘floaters’ that are difficult to flush away) Correlation with gluten intake Failure to thrive (if child) | Anti-tissue transglutaminase antibodies Small bowel biopsy |
| Chronic pancreatitis | Steatorrhoea (offensive-smelling ‘floaters’ that are difficult to flush away) | Imaging of pancreas (ideally CT scan) |
| Short bowel syndrome | Steatorrhoea (offensive-smelling ‘floaters’ that are difficult to flush away) History of small bowel resection | Exclude other diagnoses |
| Drug abuse, iatrogenic | ||
| Laxative abuse/overuse | Psychological stressors | Us+Es (hypokalaemia) Laxative screen |
| Excess alcohol intake | History of excess alcohol intake Symptoms of chronic liver disease | Investigations for chronic liver disease Liver function tests and gamma-glutamyl transpeptidase Ultrasound |
| Drugs | Recent history of drug use Common drugs that cause diarrhoea:
| None – clinical diagnosis Exclude other causes |
| Diet | Recent changes to diet, e.g. new vegetarians | None – clinical diagnosis Exclude other causes |
| Endocrine causes | ||
| Autonomic neuropathy secondary to diabetes | Symptoms of diabetes:
| Fasting blood glucose HbA1c if already diabetic |
| Hyperthyroidism | Symptoms of hyperthyroidism:
| Thyroid function tests |
| Others/rare causes | ||
| IBS | Both constipation and diarrhoea Abdominal pain and/or bloating Symptoms improve after opening bowels Correlation with stress | Rule out organic diseases Full blood count, erythrocyte sedimentation rate, coeliac screen |
| Overflow diarrhoea | Elderly History of constipation Constipation-inducing medications (e.g. codeine-based analgesia) | Rectal examination (faecal impaction) |
| Carcinoid | Flushing Wheezing Abdominal pain Cardiac symptoms (from right-sided valve problems) | 24-hour urinary 5-HIAA CT chest/abdomen |
| Radiation enteritis/colitis | Enteritis: steatorrhoea Colitis: blood in stool Both:
| Barium studies Colonoscopy with histology |
| VIPoma | Massive volumes of diarrhoea Dehydration | Raised vasoactive peptide levels Imaging (usually CT scan) Hypokalaemia |
| Whipple’s disease | Steatorrhoea Cognitive impairment, dementia Chest pain, cardiac symptoms (pericarditis) Lymphadenopathy Joint pains Fevers | Jejunal biopsy: macrophages with PAS stain-positive granules |
Hints and Tips for the Exam
Diarrhoea is a very common symptom and one that absolutely everyone will suffer from at some point in their lives. The vast majority of cases are caused by viral gastroenteritis, which is self-limiting and requires only rehydration either with water or oral rehydration therapy (such as Dioralyte).
However, various other potentially serious pathologies can also cause diarrhoea, and the characteristics of the diarrhoea and its associated symptoms can vary immensely depending on the aetiology. This is why diarrhoea lends itself particularly well to OSCEs.
What Does the Patient Mean by Diarrhoea?
The patient may be referring to the character/type of stool, frequency or volume when they refer to diarrhoea. Although definitions vary, most clinicians would agree that the following features constitutes diarrhoea:
- Amount of >200–300 mL or g per day
- Stools that are liquid/loose
- Increased frequency (more than three times a day is unusual)
Acute Versus Chronic
Again, different clinicians have different definitions of these terms. Generally, diarrhoea that persists for more than 4 weeks is deemed chronic.
‘Red Flags’
Any of the following symptoms should prompt you to request further investigations urgently:
- Rectal bleeding
- Melaena
- Weight loss
- Chronic diarrhoea
If you are in any doubt about which investigations to suggest, you can rest assured that the following will be a good answer in the vast majority of diarrhoea-related cases:
- Colonoscopy with histological analysis/biopsy: Visualising the lesion and getting a tissue sample will usually lead to a definitive diagnosis.
- Full blood count and ferritin studies: A microcytic anaemia with low ferritin levels usually indicates gastrointestinal bleeding. Severe anaemia causing symptoms and haemodynamic instability is a medical emergency that needs urgent intervention.
- Imaging: Barium studies, CT abdomen and CT colon may all be useful in certain cases, particularly if the patient is not fit enough for a colonoscopy.
Questions You Could Be Asked
Q. What are the symptoms of a VIPoma, and which investigations would you do to help you diagnostically?
Q. Name some endocrinological causes of diarrhoea.
Q. What non-gastroenterological symptoms may present in a patient with IBD?
A. The answers to all of these questions can be found in the text above.
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