Pyonephrosis laboratory findings

The initial workup done when suspecting a case of pyonephrosis include urinalysis and culture which may show white blood cells, bacteria, and pus cells; complete blood count with differentials showing neutrophilia, and blood culture which may be positive if bacteremia has already occurred. The urine and blood samples for culture must be obtained prior to starting the antibiotic therapy.

The initial workup done when suspecting a case of pyonephrosis are the following^[1][2]:

Urine samples must be collected before starting the antibiotic therapy to avoid false-negative results.

If percutaneous nephrostomy is done, the sample must be collected from the site above the obstruction

The presence of white blood cells, bacteria, pus cells in the urine may indicate pyonephrosis.

Cultures must be sent for gram stain, fungal pathogens, and acid-fast stain (if tuberculosis is suspected).

CBC with differential count should be obtained which will reveal leukocytosis with neutrophilia.

Blood samples should also be collected prior to starting the antibiotic therapy to avoid false-negative results.

Blood cultures will be positive in pyonephrosis if the infection has spread to the bloodstream.

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