Kidney stones Flashcards
Epidemiology of Kidney stones
Common
Up to 12% of men and 5% of women will develop a urinary calculus by age 70.
Aetiology of Kidney stones
the main risk factor hypercalciuria, a hereditary condition present in 50% of men and 75% of women with Ca calculi; thus, patients with a family history of calculi are at increased risk of recurrent calculi.
5 to 8% of calculi are caused by renal tubular acidosis.
About 1 to 2% of patients with Ca calculi have primary hyperparathyroidism.
Rare causes of hypercalciuria are sarcoidosis, vitamin D intoxication, hyperthyroidism, multiple myeloma, metastatic cancer, and hyperoxaluria.
Pathogenesis?
are formed when the urine is supersaturated with salt and minerals such ascalcium oxalate, struvite (ammonium magnesium phosphate), uric acid and cystine.
60-80% of stones contain calcium
They vary considerably in size from small ‘gravel-like’ stones, to large staghorn calculi. T
initial factor involved in the formation of a stone may be the presence of nanobacteria that form a calcium phosphate shell
another cause Calcium oxalate precipitates form in the basement membrane of the thin loops of Henle; these eventually accumulate in the subepithelial space of the renal papillae, leading to a Randall’s plaque and eventually a calculus
Urinary calculi may remain within parenchyma or renal pelvis or be passed into the ureter and bladder. Causing symptoms along the way.
During passage, calculi may irritate the ureter and may become lodged, obstructing urine flow and causing hydroureter and sometimes hydronephrosis.
Common areas of lodgment include the ureteropelvic junction, the distal ureter (at the level of the iliac vessels), and the ureterovesical junction.
Larger calculi are more likely to become lodged. Even partial obstruction causes decreased glomerular filtration. With hydronephrosis and elevated glomerular pressure, renal blood flow declines, further worsening renal function.
Natural History
Approximately 80-85% of stones pass spontaneously.
A stone that has not passed within 1-2 months is unlikely to pass spontaneously
Full obstruction = permanent kidney damage
Clinical Manifestations
All calculi in the renal parenchyma or renal pelvis are usually asymptomatic unless they cause obstruction and/or infection.
Severe pain, often accompanied by nausea and vomiting, usually occurs when calculi pass into the ureter, cause obstruction, or both. Sometimes gross hematuria also occurs.
Renal colic = variable intensity & typically excruciating and intermittent, often occurs cyclically, and lasts 20 to 60 min.
Nausea and vomiting are common. Pain in the flank or kidney area that radiates across the abdomen suggests upper ureteral or renal pelvic obstruction. Pain that radiates along the course of the ureter into the genital region suggests lower ureteral obstruction.
Suprapubic pain along with urinary urgency and frequency suggests a distal ureteral, or bladder calculus.
Symptoms
fever
nausea/vomitting
ashen face
foul smelling urine
renal colic = obvious pain
haematuria
Signs
The patient is apyrexial in uncomplicated renal colic (pyrexia suggests infection and the body temperature is usually very high with pyelonephritis).
Examination of the abdomen can sometimes reveal tenderness over the affected loin. Bowel sounds may be reduced. This is common with any severe pain.
There may be severe pain in the testis but the testis should not be tender.
Blood pressure may be low.
Full and thorough abdominal examination is essential to check for other possible diagnoses - eg, acute appendicitis, ectopic pregnancy, aortic aneurysm.
Complications
upper Uti,
obstruction
pyelonephritis - sudden and severe kidney infection
pyonephrosis - Pus collects in the renal pelvis and causes distension of the kidney
urosepsis - infection starts in the urinary tract and spreads into the bloodstream
surgery
Prognosis
Approximately 80-85% of stones pass spontaneously.
Approximately 20% of patients require hospital admission because of unrelenting pain, inability to retain enteral fluids, proximal UTI, or inability to pass the stone
Generally, however, in the absence of infection, permanent renal dysfunction occurs only after about 28 days of complete obstruction.
