Chapter 64: Urinary Sediment/Urinary Tract Infections

Patient Story

A 10-year-old boy presented to the office with a 2-day history of “tea-colored” urine. Two weeks prior to this presentation, he had an upper respiratory infection that resolved without treatment. Two years ago, he had a similar episode of gross hematuria that developed after a viral infection, and at that time the diagnosis of IgA nephropathy was entertained. His urine now reveals hematuria (Figure 64-1) but no proteinuria.

Introduction

Examination of the urinary sediment is a test frequently done for evaluation of patients with suspected genetic/intrinsic (e.g., systemic lupus nephritis, sickle cell disease, glomerulonephritis, interstitial nephritis), anatomic (e.g., arteriovenous malformation), obstructive (e.g., posterior urethral valves, kidney stones), infectious, metabolic (e.g., coagulopathy), traumatic, or neoplastic disease of the urinary tract. Potential findings of red or white blood cells, casts, bacteria, or neoplastic cells help in directing further evaluation of a patient's problem.

Epidemiology

• Although there is no consensus on the definition of microscopic hematuria in children, 5 to 10 RBCs/HPF are considered significant.¹

• Based on an older study (N = 8,954 unselected children ages 8 to 15 years), the incidence of microscopic hematuria found in one or more of four urine specimens was 4.1 percent; the incidence was 1.1 percent for hematuria present in two or more specimens.²

• Macroscopic (visible) or gross hematuria among children has an estimated incidence of 1.3/1000.³

• Isolated pyuria (>2 to 10 white blood cells per high-power field [WBCs/HPF]) is not uncommon in sick neonates and febrile children.

  • In a study of 110 consecutive infants admitted to a neonatal intensive care unit in Karachi, 35 had pyuria, of who 71.4 percent had no growth in urine cultures.⁴

  • In a case series of children with Kawasaki disease (KD; N = 210), 29.5 percent (N = 62) had pyuria including 34 with sterile pyuria and eight with bacterial pyuria.⁵

  • In another case series of children with acute KD compared to children with other febrile illnesses, 79.8 percent of KD and 54.0 percent of febrile children without KD had pyuria.⁶ The median number of white blood cells in the urine was higher for children with KD (42 WBC/microL vs. 12 WBC/microL in febrile children).

• Urinary tract infections (UTIs) are common in children (8% of girls and 2% of boys by age 7 years) and WBCs on microscopy have 73 percent sensitivity and 81 percent specificity for the diagnosis.⁷

  • About 60 percent of children who have a febrile UTI are found to have defects on renal cortical scintigraphy (RCS) indicating acute pyelonephritis; of these, 10 to 40 percent will have ...