Crystals

Question 1

UA: Hexagonal crystals.

Answer 1

Cystinuria = aminoaciduria. AR. Tx urine alkalinization (acetazolamide)

Question 2

UA: diamond or rhombus crystals

Answer 2

Uric acid stones
Radiolucent
Increased hydrogen ion excretion in the urine can cause formation (low urine pH), and low urine volume with high uric acid conc

Question 3

UA: rectangular prism (coffin lid)

Answer 3

Magnesium ammonium phosphate (struvite)

2nd MC - staghorn

Question 4

UA: rosettes, elongated, wedge-shaped

Answer 4

Calcium phosphate

Question 5

UA: octahedron (square with X in center)

Answer 5

Calcium oxalate

Question 6

MCC of UNILATERAL fetal hydronephrosis

Answer 6

Ureteropelvic junction obstruction

inadequate canalization of UPJ

Question 7

MCC of BILATERAL hydronephrosis

Answer 7

Posterior urethral valves in boys

Question 8

Positively birefringent under polarized light - blue parallel, yellow perpendicular

Answer 8

pseudogout (knee common)

Question 9

Negatively birefringent under polarized light - yellow parallel, blue perpendicular

Answer 9

gout (toe common)

Question 10

What factors are increased in urine conc that promote renal calculi formation? Decreased?

Answer 10

Increased - UA, Ca, oxalate

Dec - fluid, citrate (eg in met acidosis)

Question 11

Oxalate crystals in tubular lumen and proximal tubular cell ballooning with vacuolar degeneration indicates what?

Answer 11

ATN due to ethylene glycol poisoning (oxalate crystals)
Note: ethylene glycol is absorbed from GI and metabolized to glycolic acid and oxalic acid, which precip as ca oxalate crystals

Question 12

What enzyme plays a role in pigmented gallstones?

Answer 12

Beta-glucuronidase - released from injured hepatocytes –> hydrolyzes bilirubin glucuronides to unconjugated bilirubin
Note: pigmented gallstones arise secondary to bacteria or helminth infx (eg clonorchis sinensis)

Question 13

Where else on the body can tophi appear other than toe?

Answer 13

EAR
Olecranon bursa
AChiles tendon