Laxative Abuse Flashcards
Melanosis Coli
Melanosis coli
Melanosis coli is a disorder of pigmentation of the bowel wall. Histology demonstrates pigment-laden macrophages
It is associated with laxative abuse, especially anthraquinone compounds such as senna
Sx = Diarrhoea
Laxative Abuse - Example Question
A 45 year old female ITU nurse presents to the outpatient Gastroenterology clinic with a 12 week history of watery diarrhoea. She has been moving her bowels up to 9 times a day, the diarrhoea is painless and there is no blood in the stool. She said that she has also lost weight. As a nurse, she says that she regularly weighs herself and her BMI has dropped from 20 kg/m² to 18 kg/m² in the past 2 months. There is no vomiting but there is some nausea.
She also tells you that she has had two close family bereavements recently and that she is fearful of losing her job which is causing her a significant amount of stress and anxiety. As a teenager, she tells you that she had an eating disorder which required talking therapy for a period of time but that she has had no relapse for 20 years. She has a history of hypothyroidism for which she takes Levothyroxine 100mcg PO OD. She is otherwise well. She has a family history of hypothyroidism and type 1 diabetes.
Full physical examination including PR is unremarkable. Bloods show the following:
Hb 11.3 g/dl MCV 92 fl Platelets 421 * 109/l WBC 11.4 * 109/l Neuts 7.0 * 109/l
Na+ 142 mmol/l K+ 3.8 mmol/l Urea 4.8 mmol/l Creatinine 56 µmol/l CRP 16 mg/l TSH 1.67 u/l
Bilirubin 6 µmol/l
ALP 90 u/l
ALT 12 u/l
Albumin 45 g/l
Abdominal x-ray: no abnormality detected
Colonoscopy: normal mucosa to terminal ileum on visual inspection.
Considering your differential diagnosis, which two investigations would be most appropriate to perform in order to be most confident about making a diagnosis?
OGD and free T4 OGD and serum thyroglobulin Urine laxative screen and serum thyroglobulin OGD and histology of bowel biopsies > Urine laxative screen and histology of large bowel biposies
There are 3 possible diagnoses here.
She has a history of an eating disorder with weight loss and some trigger factors and access to prescription drugs. Abuse of laxatives or thyroxine could cause these symptoms. However, if she was abusive thyroxine for 12 weeks, we would expect to see TSH suppression or some physical signs. This makes thyroxine abuse much less likely (although you could do a serum thyroglobulin to confirm this).
However, abuse of laxatives is still in the differential. The other diagnosis to consider is microscopic colitis. This is more common in females (about 5:1 ratio) more common in middle age and more common in those with a personal r family history of autoimmune disease (especially hypothyroidism), OGD and colonoscopy could be entirely normal visually but the diagnosis would be revealed by an abnormal mucosa on biopsy eg lymphocytic infiltrates in the lamina propria.
Therefore E is the correct answer as it should give the diagnosis without the need for any invasive investigation
