A straight-forward pyelonephritis can turn out more complicated than you expect.
You are early in your shift and still a little preoccupied with the group’s quarterly performance report posted earlier in the day. Perhaps most damaging to your ego, the “patients per hour” metric placed you at the 25th percentile, the lowest you’ve scored. For today’s first few encounters, you emphasized time-efficiency and patient-flow. Some of your more senior residents, also included in the performance report, seemed to get the unspoken message that speed was going to be your focus of the day and stepped-it-up accordingly.
One of your residents approaches and begins to present what his non-verbal cues suggest will be a straight-forward case. “I have a 6-year-old girl who has presented with fever of 39.90 Centigrade following two days of left flank pain. Her urine dipstick is positive for leukocyte esterase while she appears otherwise well. She has normal, age-appropriate, vital signs and left lower flank tenderness; otherwise, her exam is unremarkable. She has never before had a urinary tract infection. She has not had vomiting and has tolerated oral fluids. I have cultured her urine and am going to discharge with a prescription for our usual oral antibiotic pending follow-up with her PCP on Monday.”
“Hmmm.” You think to yourself, “Do I have to be such a Grumpy Gus?… Yes.”
“Did you do a bedside ultrasound to look for evidence of a stone?”
Your resident’s reaction suggests you have abandoned a New Year’s resolution before Times Square has cleared. “Well, no.”
Sounding every bit the super-compulsive physician, you respond, “Renal stones are associated with a small but meaningful proportion of urinary tract infection in children. Non-detection of stones can actually risk urosepsis as well as renal parenchymal damage.” You barely manage to avoid adding something to the effect of, “I know, I can make even a straight-forward pyelonephritis complicated.”
Image demonstrates a normal right kidney.
Illustrates moderate hydronephrosis of the left kidney consistent with obstruction.
You and your resident walk, uncomfortably, over to the patient’s room and mention to her mother that you’d like to do a little more investigative work before considering discharge. Her left kidney is slightly larger than the right (Figures 1, 2 above). You proceed distally and spend some time assessing both ureterovesicular junctions. You notice fairly frequent ureteral jets on the right but none on the left (Figure 3 below). You focus on the ureterovesicular junction and discover a 5-millimeter radio-opaque density with posterior shadowing (Figure 4 below).
Color doppler demonstrates a normal right ureteric jet in contrast to a stone (arrow) and an obstructed jet effect at the left ureterovesicular junction.
Left Ureterovesicular junction stone (arrow).
During your time in the patient’s room, you learn that she recently sustained a femur fracture playing soccer and experienced a protracted period of immobility. In addition, the child’s father has a history of renal stones.
You subsequently counsel the mother that you would prefer to admit her child for hydration as well as possible additional assessment. Lab values, including BUN and creatinine, are normal for a 7-year-old but you remain firm in your desire to admit and administer the first dose of intravenous antibiotic prior to the patient’s departure for the inpatient ward.
DX: Specialist recommends timely removal of stone
Following admission, the child continued to receive intravenous antibiotics and isotonic fluid. Chemical analysis demonstrated increased urinary excretion of calcium. As expected, a repeat consultative ultrasound revealed no movement of the stone from its previous location near the ureterovesicular junction with continued ipsilateral hydronephrosis and absence of ureteric jets.
Because of the relatively large size of the stone, its proximity to the ipsilateral ovary and the co-existing infection, the urologist advised timely removal via ureteroscopy as opposed to extracorporeal shock wave lithotripsy (ESWL) and/or percutaneous nephrostolithotomy (PCNL). A calcium oxalate monohydrate stone was removed and post-operative recovery was uneventful. The child experienced no stone recurrence following the institution of a low-calcium diet and resumption of normal physical activity.
Pearls and Pitfalls: Using Ultrasound to Detect Nephrolithiasis
- Most emergency physicians are aware that children experience kidney stones. What many emergency physicians do not consider is that a small proportion of children with urinary tract infections have concomitant nephrolithiasis.
- All children with urinary tract infection should be assessed for possible nephrolithiasis. Stones can be either the cause or the result of urinary tract infection while sustained clearance of infection with antibiotic therapy alone in the presence of nephrolithiasis is difficult.
- “Pus under pressure” is an indelicate but accurate metaphor that communicates the potential for urosepsis associated with an obstructing stone. Delivery of the antibiotic to the site of infection may be attenuated by decreased glomerular filtration resulting from a diminished pressure gradient across the basement membrane. In addition, renal parenchymal damage may result from persistent obstruction.
- Definitive treatment strategies are specific to the urologist’s preference and experience as well as various possible patient characteristics. In general, immediate surgical intervention to effect removal occurs (a) when the stone is large (> 5 mm diameter) and unlikely to pass spontaneously, (b) when lab values reflect acute renal insufficiency, (c) in the presence of co-infection, and (d) when there is evidence for complete obstruction. The persistent ipsilateral absence of ureteric jets on serial bedside sonograms can provide corroborating information. In addition, signs of incomplete obstruction in a patient with only one kidney is considered an absolute indication for immediate surgical stone removal.
- Due to the higher spontaneous passage rate for smaller calculi, an observation period of up to 2 weeks employing the alpha blocker tamsulosin and pain control is often utilized in the absence of indications for immediate surgical stone removal.
- There are multiple urologic options for stone removal in children. Included are extracorporeal shock wave lithotripsy (ESWL), percutaneous nephrostolithotomy (PCNL) and ureteroscopy, with or without stenting. ESWL delivers high energy shock waves intended to effect fragmentation of stones with resultant spontaneous passage of smaller particles. It has been shown to be effective and safe in small children and infants for stones of less than 2 mm diameter. However, for larger and harder stones the definitive success rate is less. Moreover, ESWL use is often avoided for distal ureteral stones in females due to proximity to the ipsilateral ovary.
- Percutaneous nephrostolithotomy was adapted to pediatric patients in the 1990s and is a more invasive procedure requiring access to the collecting system and tract dilatation prior to physical extraction of a stone. Consistent with any invasive procedure, complications include infection, bleeding, perforation and injury to adjacent organs.
- Ureteroscopic stone removal has benefitted from the advent of flexible and miniaturized instrumentation. It is considered a first-line therapy for pediatric patients at or above 5 years of age and is particularly useful for the removal of ureteral stones less than 10-millimeters diameter.
- In our experience, the bedside sonographic assessment for possible nephrolithiasis in children with urinary tract infection is well-worth the time utilized. Significant calcium-containing stones at the ureteropelvic and ureterovesicular junctions may be visualized directly as may ureteral stones at the level of the pelvic brim. On occasion, even radiolucent stones may be detected via notice of so-called “twinkle-artifact,” which appears due to refraction of sound waves within a crystalloid matrix (Figure 5 below). The sonographic absence of ureteral jets in the presence of an ipsilateral dilated kidney is an indirect but worrisome finding that should alert clinicians to the potential for significant complications in situations where a stone is possible.
Twinkle artifact distal to left ureterovesical junction stone (arrow).
- Although beyond the scope of the present article, it should be mentioned that guidelines for the diagnostic evaluation of possible nephrolithiasis in children advocate a staged approach using ultrasound first. Some speculate that even a single non-contrast stone-protocol computed tomography (CT) exam may increase a child’s risk for subsequent abdominal/pelvic cancer while the majority of cases of pediatric nephrolithiasis are manageable without CT.1 We will review various diagnostic strategies for suspected renal stones in a forthcoming segment of Soundings.
REFERENCE
- Are Stone Protocol Computed Tomography Scans Mandatory for Children with Suspected Urinary Calculi? Johnson EK, Faerber GJ, Roberts WW, et. al. Urology 78(3):662-666, 2011.