10. Calculi

Question 1

why do calculi form

Answer 1

Form when urinary conc. of particular material increases to point that it begins to precipitate and form crystal aggregates

Question 2

name different substances that can form calculi - which is most common

Answer 2

1. calcium oxalate (more common) or calcium phosphate (or both): often formed in conditions that increase blood calcium and thus urinary calcium (e.g. famililal hypercalciuria, hyperparathyroidism, sarcoidosis, some malignancies)
2. Uric acid: eg in gout Ps or myeloproliferative diorders (release of nucleid acids after cytotoxic drugs forms uric acid stones)
3. Struvite
4. Cysteine

Question 3

where do calculi form

Answer 3

1. renal pelvis and calyces (most common) - can be staghorn or non-staghorn
2. ureters
3. bladder

Question 4

name the 2 main presenting symptoms/signs for calculi

Answer 4

1. Ureteric colic (as stones passes down ureter) - intense episodic flank pain likely resulting from peristaltic attempts by ureters to push urine past obstructing stone. Often radiates to hypochondrium or groin.
2. Haematuria

Question 5

name 2 possible complications of calculi

Answer 5

90% are successfully passed, but some may cause urinary tract obstruction by blocking urine outflow…

1. infection (UTI) by providing nidus for bacterial growth
2. post-renal AKI (staghorn calculi can silently destroy renal function without early clinical consequences)

Question 6

describe the management options for RENAL calculi

Answer 6

1. conservative: wait for stones to pass (often <3 wks)
2. non-invasive: extracorporeal shockwave lithotripsy
3. invasive management: cytoscopy + ureteroscopy (URS) + lasertripsy or percutaneous nephrolithotomy