IBD

Question 1

CD renal stones

Answer 1

calcium oxalate and uric acid

Calcium oxalate stones form when the ileum is affected, preventing proper absorption of fats. Unabsorbed long-chain fatty acids compete with the insoluble calcium oxalate for calcium. Without calcium, oxalate binds sodium, becomes soluble, is absorbed by the colon (“enteric hyperoxaluria”), and eventually re-precipitates as calcium oxalate stones when excreted in the urine. Calcium is an effective treatment. Uric acid stones form secondary to bicarbonate loss with diarrhea. With low serum bicarbonate, the kidneys excrete acid in compensation. Uric acid, which is soluble in alkalotic conditions, precipitates as stones in the low pH urine.
Question

Question 2

Which 5-ASA involves coating 5-ASA with resins or microgranules, which dissolve and release 5-ASA in settings of pH>7 (distal small bowel and colon).

Answer 2

Pentasa and Asacol

Question 3

Which 5-ASA involves dimerizing 5-ASA, so that it is only released after bacterial cleavage (in the colon)?

Answer 3

Olsalazine (Dipentum)

Question 4

Idiosyncratic Rxn (dose-dependant) of AZA and 6-MP

Answer 4

Pancreatitis, fever, rash, and pneumonitis

Question 5

Leukopenia with 6-MP

Answer 5

Leukopenia occurs when the 6-MP metabolites are shunted away from TPMT-mediated production of 6-MMP (which causes hepatotoxicity). Instead, 6-MP is metabolized through a different pathway to 6-TG. 6-TG accumulates in tissues, inhibits purine metabolism and subsequent DNA/RNA synthesis, and prevents lymphocyte proliferation. If too much, 6-TG can cause severe leukopenia and dangerous host immunosuppresion