Home Medicine PA Boards 75: Microscopic Hematuria Workup

PA Boards 75: Microscopic Hematuria Workup

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Today we’re going to discuss the workup needed when presented with asymptomatic microscopic hematuria. Let’s discuss the history, physical exam, and labs that need to be ordered.

Most children who present with microscopic hematuria will have a benign etiology. But, who needs to be worked up and who doesn’t?

Microscopic hematuria is defined as the presence of more than five RBCs per high-power field. Microscopic hematuria may be discovered as an incidental finding on a urinalysis.

False-negative results can occur in the presence of high urinary concentration of ascorbic acid. False-positive results may occur with alkaline urine.

(Hgb check before UA can lead to blood in urine during a physical exam)

After positive dipstick you want to send the urine for analysis. The absence of RBCs and RBC casts despite a positive dipstick test suggests hemoglobinuria or myoglobinuria.

Lets assume it’s still positive. After sending the urine for analysis and having a positive result, the next step is to figure out if this is a glomerular cause or non glomerular cause. Red cell casts are pathognomonic for glomerular disease.  Dysmorphic RBC and protein in the urine also point to a glomerular cause.

The absence of these findings doesn’t prove anything one way or the other.

Always make sure to retest the urine. 75% will resolve after repeat testing. 63% of those which didn’t resolve will resolve after 6 months of repeat testing.

For those that don’t resolve, this is termed persistent hematuria – hematuria present after 6 months.

If the patient is asymptomatic – then you may continue to retest. The most common causes of persistent microscopic hematuria include glomerulopathies, hypercalciuria, and nutcracker syndrome.

Nutcracker syndrome: left renal vein compression between the aorta and proximal superior mesenteric artery. This may also be associated with left flank pain.

Typically you can just observe these children and repeat the UA so long as the patient is asymptomatic, there’s nothing in the history, and the physical exam is normal. Things that would prompt a workup include hypertension, proteinuria, or gross hematuria.

Vigorous exercise can lead to hematuria.

Other things that would prompt a diagnosis are (pulled from Medscape)…

•Fever, abdominal pain, dysuria, frequency, and recent enuresis in older children may point to UTI.

•Recent trauma to the abdomen may be indicative of hydronephrosis

•Early-morning periorbital puffiness, weight gain, oliguria, dark-colored urine, and edema or hypertension suggest a glomerular cause

•Hematuria due to glomerular causes is painless

•Recent throat or skin infection may suggest postinfectious glomerulonephritis

•Joint pains, skin rashes, and prolonged fever in adolescents suggest a collagen vascular disorder

•Anemia cannot be accounted for by hematuria alone; in a patient with hematuria and pallor, other conditions should be considered

•Skin rashes and arthritis can occur in Henoch-Schönlein purpura and systemic lupus erythematosus

•Information regarding exercise, menstruation, recent bladder catheterization, intake of certain drugs or toxic substances, or passage of a calculus may also assist in the differential diagnosis

•A family history that is suggestive of Alport syndrome, collagen vascular diseases, urolithiasis, or polycystic kidney disease is important

The physical examination should look for edema and recent weight gain, skin examination (purpura), direct visualization of the genitals looking for penile urethral meatal erosion or female introitus pathology, and evaluation for abdominal discomfort or masses (Wilms’ tumor).

Let’s say the exam is negative and the history is negative. Send out for a culture to rule out UTI. If positive, treat with antibiotics

If negative and asymptomatic, continue to recheck the urine every 3-6 months. If hematuria persists for a year, then a more thorough workup should be done.

The next step is to to rule out hypercalciuria and order a renal ultrasound to rule out stones, tumor, and possible nutcracker syndrome (this requires a doppler ultrasound). Remember, CT scan is not the initial test of choice in children when evaluating stones because of the radiation.

Other labs that can be ordered include serum creatinine, complete blood count, C3, C4, serum albumin, and ANA. But, I would honestly refer these patients to a nephrologist.

There you have it!

Andrew

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