Hematuria and Renal Stones Flashcards
Definition of Hematuria
Defined as abnormal presence of erythrocytes in urine. They may of normal morphology or damaged; they may originate from any site in the urinary tract, from GBM to the distal urethra. Hematuria at low levels that does not change appearance of urine and is detected only by microscopy or dipstick analysis is termed microscopic hematuria. These dipsticks can detect as few as 1-2 RBC’s per HPF (40x lens) in unspun urine and more than 2-3 RBC’s/HPF defines micro-hematuria.
Substances other than blood that can make the urine red…
•Drugs
- pyridium
- rifampin
- phenolphthalein
- nitrofurantoin
- chloroquine
•Foods
- beets
- blackberries
- red food coloring
•Metabolites
- bile pigments
- melanin
- meth-hemoglobin
- porphyrin
- extracellular hemoglobin
- myoglobin
Major Categories of Disease
- Infections
- Kidney STones
- Cancer
- Glomerular Disease
•benign causes:
- mestruation
- mild trauma
- vigorous exercise
Infection
Infection is an unusual cause of isolated hematuria, since pyuria is almost always present. Cystitis may or may not be symptomatic, but pyelonephritis is usually accompanied by flank pain and fever. Infections can complicate other causes of hematuria, e.g. cancer and stones.
Kidney Stones
Stones are a common cause of hematuria Patients may have no symptoms, a history of having passed stones or gravel, or present with acute flank pain that radiates into the ipsilateral groin. The latter presentation suggests that the stone is passing through the ureter and causing obstruction and spasm. Stones smaller than 4 mm may pass through the collecting system on their own. Stones larger than 4 mm may require urological intervention. The best diagnostic test for stones is imaging with non-contrast CT. About 12 % of men and 5 % of women will have a kidney stone at some point in their life. There is an increasing prevalence with age and location. The Southeastern US is considered the “stone belt” given the higher prevalence in this part of the country.
- calcium
- sturvite
- uric acid
- cystine
Calcium Stones
Calcium stones make up about 75% of all stones, with calcium oxalate more common than calcium phosphate. Patients with hypercalciuria, hyperoxaluria and/or hypocitraturia are at risk for calcium oxalate stones. Often the cause of hypercalciuria is unknown, but an investigation may reveal underlying cause like primary hyperparathyroidism. High concentrations of calcium in the urine are seen in individuals with low fluid intake and a diet rich in salt. Hyperoxaluria may occur in individuals on a high oxalate or low calcium diet. Calcium binds oxalate in the gut and limits its absorption. Fat malabsorption syndromes can also lead to hyperoxaluria by binding GI calcium. Citrate is a urinary inhibitor of crystal formation. Reduction in urinary citrate may not have an explanation but also occurs in distal renal tubular acidosis. Individuals on a high animal protein diet also have low urinary citrate levels.
Sturvite Stones
Sturvite stones are composed of magnesium ammonium phosphate and only develop in patients with chronic infections with urea splitting organisms that produce urease, eg klebsiella and proteus. Urea —> 2NH3 + CO2 NH3 + H2O —> NH4+ + OH
High urinary levels of NH4 and high urine pH permit struvite formation. Struvite crystals tend to form stones in the renal pelvis called staghorn calculi.
Uric Acid Stones
Uric acids stones form in a low urine pH, and are not opaque on a standard KUB. They occur in patients with gout and in obese patients with or without diabetes.
The crystals can have multiple shapes but a rhomboid shape is most common (hard to hang your hat on a uric acid crystal).
These stones occur in patients with chronic diarrhea because the GI bicarbonate and fluid losses lead to a low urine volume and pH.
Cysteine Stones
Cystine stones are due to an autosomal recessive defect in the cystine transporter in the proximal tubule that impairs normal reabsorption and leads to cystinuria. These patients may pass their first stone as a child. The stones are less opaque on a standard KUB than calcium stones. The crystals have a characteristic hexagonal shape.
Cancer
- Cancer is more likely to be the explanation for hematuria in patients over the age of 40.
- Gross hematuria is more often associated with cancer than microscopic hematuria.
- Bladder cancer is the most common followed by kidney and upper tract malignancies.
- Everyone with isolated hematuria needs imaging of the urinary tract for cancer.
- Contrast enhanced CT scans are excellent at picking up renal masses and afford an opportunity to look at the collecting system. The sensitivity and specificity of IVP and ultrasound are considerably lower than CT for renal masses and ultrasound will not evaluate the collecting system at all.
- Bladder cancer can best be detected by combining urine cytology and cystoscopy. All patients over the age of 40 with isolated hematuria should have screening for bladder cancer.
- Other risk factors that should prompt evaluation for bladder cancer include smoking, a positive family history, a history of chronic infections or exposure to radiation or cyclophosphamide.
Glomerular Disease
- coca - cola colored urine
- Clots also suggest extraglomerular hematuria. RBCs that have passed through the glomerular filtration barrier and made their way through the renal tubular array of osmolarity often are dysmorphic.
- RBCs may become trapped in the gelatinous protein matrix of the distal renal tubule and form RBC casts. RBC casts are indicative of glomerular bleeding.
- The appearance of RBCs and protein in the urine strengthens the likelihood of a glomerular disease.
- IgA Nephropathy
- Familial Hematuria
- Alport’s Syndrome
- other mild focal glomerulonephritis
IgA Nephropathy
- IgA nephropathy can present as gross hematuria, isolated microscopic hematuria or a nephritic syndrome with hypertension and renal failure.
- The deposits of IgA in the glomeruli result from increased production, impaired clearance, and/or abnormal glycosylation of circulating IgA.
- The IgA is mainly deposited in the glomerular mesangium causing mesangial cell proliferation on light microscopy. Immune fluorescence confirms that the immunoglobulin doing the damage is IgA.
Benign Familial Hematuria aka Thin Basement Membrane Disease
- The prevalence of this disorder may be as high as 5%. It has an autosomal dominant mode of inheritance, so it is easy to screen the urine of family members to support the diagnosis.
- The genetic defect is in the alpha 3 and alpha 4 chains of type IV collagen in the glomerular basement membrane.
- There are no extrarenal manifestations and the prognosis is excellent.
- This diagnosis requires biopsy and examination of the electron micrographs.
Alport’s Syndrome
- Alport’s syndrome is another form of hereditary nephritis that may present as isolated hematuria. This syndrome occurs in 1 in 50,000 live births.
- It is also a type IV collagen nephropathy but the defect in this case is in the alpha 5 chain.
- There is often associated neural hearing loss and ocular abnormalities.
- The mode of inheritance is x-linked in the majority (80%), but there are both autosomal recessive and dominant variants.
- The glomerular basement membrane in Alport’s syndrome demonstrates variable regions of thick and thin membrane with fraying (basket-weave appearance).
- Some patients, usually males in the x-linked variety, may develop renal failure.
