At a Glance

Acute pyelonephritis results from bacterial invasion of the renal parenchyma. Escherichia coli accounts for 70-90% of uncomplicated urinary tract infections and 20-50% of complicated infections.

Patients demonstrate a wide range of presentations with pyelonephritis, ranging from a mild illness to sepsis. Patients usual present with fever, flank or back pain, shaking chills, and irritation related to bladder voiding. Typically, the irritation can be described as urgency, frequency, or dysuria. Associated with the disease is nausea, vomiting, or diarrhea. Signs include fever, tachycardia, and pronounced costovertebral angle tenderness.

Acute pyelonephritis may be life-threatening or cause loss or permanent scarring of a kidney. Two thousand five hundred cases occur in the United States each year with 200,000 patients requiring hospitalization.

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What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

Gross hematuria occurs infrequently with pyelonephritis being more common with lower urinary tract infections, such as hemorrhagic cystitis.

Pyuria, which is defined as more than 5-10 white blood cells (WBCs) per high-power field, is present in almost all patients with pyelonephritis. Usually, there are more than 20 WBCs/high power field in acute cases, with lower numbers in subacute cases.

The dipstick leukocyte esterase test (LET) is useful in screening for pyuria and is aided by the nitrite production test (NPT). Combined, they have a sensitivity of 79% and specificity of 81%.

The urine microscopic examination may show hematuria, but hematuria is nonspecific. White cell casts are suggestive of pyelonephritis.

Proteinuria is expected up to 2 grams/day. If proteinuria exceeds 3 grams/day, one should suspect glomerulonephritis. The presence of bacteria on microscopic examination is suggestive but may be present in lower urinary tract infections.

Urine culture is indicated in any patient with pyelonephritis, especially to screen for antibiotic resistance.

Blood cultures are indicated in any patient who had been or is in the process of being admitted. Approximately 12-20% of blood cultures are positive in acute glomerulonephritis. (Table 1)

Table 1
Complete Blood Count (CBC) Urinalysis Urine Culture Blood Culture
leukocytosis with left shift pyruria, bacteria, variable amounts of hematuria, occasionally with white casts heavy growth of E. coli may be positive

Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications – OTC drugs or Herbals – that might affect the lab results?

Antibiotics, such as aninoglycosides, beta-lactams, and quinolones, may interfere with urine and blood cultures.

What Lab Results Are Absolutely Confirmatory?

Positive urine cultures confirm the presence of a urinary tract infection. Renal ultrasound helps localize the lesion.

Hematuria can be caused by other diseases, such as glomerulonephritis, lupus, diabetes mellitus, Goodpasture’s syndrome, polyarteritis nodosa, hemolytic uremic syndrome, physical conditions of kidneys, such as stones or trauma, bladder neoplasms, bladder stones, cystitis, urethritis, urethritis, Schistosomiasis, diverticulitis, pelvic inflammatory disease, and appendicitis.

What Confirmatory Tests Should I Request for My Clinical Dx? In addition, what follow-up tests might be useful?

The following should be ordered:

CBC (absolute leukocyte count)

Urinalysis with microscopic

Urine culture

Blood culture

What Factors, if Any, Might Affect the Confirmatory Lab Results? In particular, does your patient take any medications – OTC drugs or Herbals – that might affect the lab results?

The findings in pyelonephritis can be nonspecific. The degree of pyuria and hematuria does not correlate with the severity of symptoms.