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home - Colon - Diagnostic Pathways for Colonic Disease - Difficult Diarrhoea Written by Dr Sebastian Zeki
Methods GMP
Knows the physiology of intestinal absorption, secretion and motility SCE 1
Understands the biochemical processes occurring within the gut
lumen and at mucosal level

Has awareness of the factors controlling these processes – in
particular the neuro-endocrine influences

Understands the range of mechanisms by which diarrhoea can result
from disturbances in each of these processes

Knows the causes of both acute and chronic diarrhoea
Knows the range of investigations appropriate to determining the
cause of the patient’s diarrhoea and is aware of the range of
therapeutic possibilities

Makes a detailed clinical assessment of patients that present with
either acute or chronic diarrhoea

Recognises the potential need for urgent fluid replacement CbD,
Makes appropriate use of microbiology and other relevant laboratories in reaching a diagnosis

Shows ability to interpret results, reach a diagnosis and formulate a
treatment plan

Reacts appropriately to the urgency of the clinical presentation
Always shows sympathy and understanding especially when the
patient is distressed

Difficult Diarrhoea

-Malnutrition, dehydration, and hypokalemia can all cause lethargy and muscle weakness-Electrolyte disturbance:-Volume depletion-Hypokalaemia (secondary hyperaldos-teronism and diarrhoea)-Metabolic alkalosis as hypokalaemia can impair reabsorption of chloride to the chlo-ride- bicarb exchange pump doesnt work and bicarb is conserved-Hypermagnesemia can occur if using a Mg-containing cathartic BO 10-20x/day 24-hour stool volumes of 300 to 3000 mL. Malabsorption The detection of chemical laxatives-[Serum] is low, (peaks 2hrs post ingestion).-[Urine] - gives the best yield and can be 10x > [plasma].-Phenolphthaleins and bisacodyls can be detected by by spectrophotometric or chromatographic assays.-Repeated analyses of stool and urine is wise, since patients may ingest laxatives intermittently. 4 months Cathartic colon Rare but severe manifestation of prolonged laxative use.It is characterized by dilation of the entire large bowel but worse on right. Room searchIt is considered as a diagnostic proce-dure which requires informed consent from the patient. Melanosis coli -Occurs witihn 4 months of onset of onset of ingestion of anthraquinone-containing laxatives Disappear in 4 months if discontinuedEvident in the rectum and sigmoid colon, although the entire colon is involved.If not evident on endoscopy, melanosis coli is demonstrated histologically by finding pigment in the macrophages of the lamina propriaIs not specific to exposure to anthraquinone laxatives Endoscopic or radiologic examination Stool analysisOsmolal gap= 295-2(K+Na).> 50 mosmol/kg can be due to unmeasured solute eg Mg, sorbitol, lactose, or lactulose in laxative.Stool [Mg] >108 mg/dL (45 mmol/L or 90 meq/L) suggests magnesium-induced diarrhoea.If stool osm.< plasma then water is being added.If stool osm.very much > plasma then urine may have contaminated stool- check stool water urea and creatinine.Osm.can increase if stool not examined quickly (bacterial breakdown of carbohydrates). Definition:Either not really true or self-induced.-Laxative abuse most common cause (15%) Difficult Diarrhoea Factitious Diarrhoea Patient characteristics90% are female.Patients areMedical/ highly educated.There is a higher incidence of anorexia nervosa. Laxative abuse Manifestations:BO 10-20x/day.24-hour stool volumes 300-3000 mL.50 % of patients complain of nocturnal bowel movements.Crampy abdominal pain (direct laxative effect).Weight loss. Some laxatives have a direct inhibitory effect on nutrient absorption eg rhein (an anthraquinone) and bisacodyl (a diphenolic laxative) impair glucose absorption+ mild steatorrhea and GI protein loss. Written by Dr Sebastian Zeki

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