2025 – PAGE 379 – NEPHROLOGY

WBC CASTS

WBC casts are associated with INTERSTITIAL NEPHRITIS and PYELONEPHRITIS.

RBC CASTS

RBC casts are associated with GLOMERULONEPHRITIS.

URINARY CRYSTAL IDENTIFICATION

Urinary crystals may be identified by shape and color. The type of crystal noted can help you identify a disorder.

• URIC ACID CRYSTALS: Seen in breast-fed babies and is harmless! It can also be associated with rapid cell turnover and hyperuricemia (as seen in lymphomas).
  • PEARL: Look for a breast-fed baby presenting with a pink spot in the diaper! Uric acid turns to a salmon- or pink-colored powder when it dries. It scares parents to heck but only requires reassurance.
  • IMAGE: www.pbrlinks.com/URICACID1
• CYSTINE CRYSTALS: CYSTEINURIA cause nephrolithiasis. Stones are made of cystine, and cystine crystals can be seen on urine microscopy.
  • IMAGE: www.pbrlinks.com/URINARYCRYSTAL1
  • MNEMONIC: “6-teinuria.” The cystine crystals are hexagons.
• STRUVITE CRYSTALS: Crystals are associated with urinary tract infections from urease-producing organisms that cause staghorn calculi,such as Proteus species (most common), Klebsiella species, Pseudomonas species, and Enterobacter species.
  • IMAGE: www.pbrlinks.com/URINARYCRYSTAL2
  • MNEMONIC: The crystals look like coffin lids. They also look like “U” in strUvite crystals.
• (DOUBLE TAKE) CALCIUM OXALATE CRYSTALS: Calcium oxalate stones are the most common ones in humans. There are two types of calcium oxalate crystals. One is square and looks like it has an X on it. That one is very common. The other is elongated and looks like a rod. The long one is the one usually associated with ethylene glycol poisoning.
  • IMAGE: www.pbrlinks.com/CALCIUMOXYLATE1
    • MNEMONIC: calcium oXalate crystals look like a big X on a crystal.
  • IMAGE: www.pbrlinks.com/CALCIUMOXYLATE2 (This one is related to ethylene glycol and kind of looks like a long can of beer or needles.)

UROLOGY, OBSTRUCTIONS, AND MASSES

URETEROPELVIC JUNCTION OBSTRUCTION (UPJ OBSTRUCTION)

Ureteropelvic junction obstruction (UPJ obstruction) is the most common cause of urinary obstruction in children, and it is associated with an increased risk of UTI. It is often suggested on ultrasound by dilated renal calyces, pelvis, or frank hydronephrosis. Children may be born with signs of oligohydramnios. After a postnatal ultrasound to confirm the findings, a voiding cystourethrogram (VCUG) should be done to rule out other anomalies and to look for reflux from the bladder into the renal pelvis due to posterior urethral valves (PUV). Once that’s been ruled out, a MAG3 furosemide renal scan (AKA renogram) is done to look for slow flow of urine from the renal pelvis into the ureter. That is the definitive test to make the diagnosis.

PEARL: The MAG3 furosemide obviously uses a diuretic and should only be ordered in patients with UNILATERAL hydronephrosis. If the patient has BILATERAL hydronephrosis, do NOT order it because you will make the problem worse.