Acute Lobar Nephronia: A Case Report and Literature Review

The Journal of Emergency Medicine, Vol. 46, No. 5, pp. 624–626, 2014 Published by Elsevier Inc. Printed in the USA 0736-4679/$ - see front matter

http://dx.doi.org/10.1016/j.jemermed.2013.08.097

Clinical Communications: Adults ACUTE LOBAR NEPHRONIA: A CASE REPORT AND LITERATURE REVIEW Sean P. Conley, DO, LCDR MC (FS) USN and Kenneth Frumkin, PHD, MD Emergency Medicine Department, Naval Medical Center Portsmouth, Portsmouth, Virginia Corresponding Address: Sean P. Conley, DO, LCDR MC (FS) USN, Emergency Medicine Department, Naval Medical Center Portsmouth, 620 John Paul Jones Circle, Portsmouth, VA 23708

, Abstract—Background: Patients with fever, vomiting, and abdominal pain commonly present to the emergency department, often generating a broad differential diagnosis. We describe the first reported case in the emergency medicine literature of acute lobar nephronia (ALN). Objectives: To describe the presentation, evaluation, and management of acute lobar nephronia. Case Report: A healthy 27-yearold woman presented after 18 h of fever to 39.94 C (103.9 F), nausea, vomiting, and severe right-sided abdominal pain. Despite a normal urinalysis, a contrasted computed tomography scan of the abdomen and pelvis demonstrated right perinephric stranding, which was initially interpreted as pyelonephritis. A staff over-read the following day by a radiology body specialist confirmed ‘‘likely developing abscess,’’ consistent with the diagnosis of acute lobar nephronia. Conclusion: A normal urinalysis may move clinicians to dismiss a nephrogenic or urologic process. ALN is considered a midpoint in the spectrum of upper urinary tract infections between acute pyelonephritis and intrarenal abscess. Diagnosis may be difficult, and inpatient management, sometimes prolonged, is the norm. Published by Elsevier Inc.

A negative urinalysis (UA) usually drives the diagnostic evaluation away from the genitourinary (GU) system. We present a case of lobar nephronia with a normal UA requiring inpatient management, not previously reported in the emergency medicine literature. CASE REPORT A previously healthy 27-year-old woman presented to the ED after 18 h of fever to 39.94 C (103.9 F), nausea, vomiting, and severe right-sided abdominal pain. Her temperature was 38.39 C (101.1 F), heart rate 101 beats/min, blood pressure 114/62 mm Hg, respirations 18 breaths/ min, and oxygen saturation 99% on room air. Physical examination demonstrated a tender right abdomen with right lower quadrant guarding, positive Rovsing sign, a positive heeltap, and right costovertebral angle tenderness. There were no abnormalities or tenderness on pelvic examination. Laboratory evaluation was remarkable only for a white blood cell count of 14,300 (97% neutrophils). UA was negative for nitrites, leukocyte esterase, or bacteria, with one red cell, two white cells, and three epithelials. A computed tomography (CT) scan of the abdomen and pelvis with intravenous contrast looking for acute appendicitis was interpreted as showing a normal appendix and right-sided perinephric stranding consistent with pyelonephritis. The patient received an intravenous dose of ceftriaxone and was discharged on oral ciprofloxacin. At her scheduled 24-h return, she was still febrile to

, Keywords—lobar; nephronia; pyelonephritis; abscess; nephromegaly

INTRODUCTION Patients with fever, vomiting, and abdominal pain commonly present to the emergency department (ED). Reprints are not available.

RECEIVED: 28 March 2013; FINAL SUBMISSION RECEIVED: 30 July 2013; ACCEPTED: 17 August 2013 624

Acute Lobar Nephronia

39.6 C (103.2 F). A staff radiologist over-read of the previous night’s CT scan was ‘‘pyelonephritis with likely developing abscess.’’ A representative image from our patient’s scan is presented in Figure 1. She was started on piperacillin-tazobactam and admitted to the Internal Medicine service. Urine cultures were subsequently positive for Escherichia coli sensitive to ampicillin. After 5 days of intravenous antibiotics, she was discharged on amoxicillin-clavulanate, and was asymptomatic on subsequent outpatient follow-up. DISCUSSION Our patient had acute lobar nephronia (ALN). Also known as acute focal bacterial nephritis, ALN is ‘‘an acute localized non-liquefactive infection of the kidney caused by bacterial infection. The main manifestations consist of fever, chills, abdominal pain, flank pain, and tenderness and percussion pain of the costovertebral angles’’ (1). Perceived as a pathologic process halfway between uncomplicated pyelonephritis and renal abscess, our patient’s CT reading of ‘‘likely developing abscess’’ also supports the diagnosis of ALN. ALN is a radiologic diagnosis first described in 1979 (2). The frequency of reported cases increased as renal imaging became more common. The cause is primarily ascending infection with E. coli, but Gram-positive organisms and hematogenous spread have also been implicated. Other pathogens include Proteus mirabilis, Klebsiella spp, Pseudomonas aeruginosa, and enterococci (3). ALN is found in previously healthy adults and children as well as those with GU abnormalities, immunosuppression, recent inappropriate treatment of pyelonephritis, or underlying comorbidities (e.g., diabetes, cirrhosis). Children predominate in published series.

Figure 1. Acute right-sided lobar nephronia (focal wedgeshaped renal hypodensity) on intravenous-contrasted computed tomography scan.

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Clinically, patients appear ill. GU symptoms and pyuria may be absent. Adults complain of fever, chills, flank, and abdominal pain. Up to two-thirds may be vomiting. Dysuria may or may not be present. Seventy-three percent of adults in a case series by Li and Zhang presented without pyuria (1). Complete blood count and C-reactive protein are often elevated, and blood and urine cultures are frequently positive. The most common presentation in children is fever, with or without flank or abdominal pain. Whereas ALN is found in up to 19% of children admitted for urinary tract infection and fever, pyuria was absent in 28–69% of children in other series (4–6). Affected children are typically older than 1 year, with underlying GU abnormalities, and have higher peak temperatures for longer durations prior to admission. Ninety percent are infected with E. coli (4). Contrast CT is the gold standard for the diagnosis of ALN, which typically appears as a poorly defined striated or wedge-shaped lesion with decreased enhancement. Figure 1 demonstrates the characteristic focal hypodensity in our patient’s right kidney. Renal ultrasound can be helpful, and was positive in 62–90% of CT-proven cases (7,8). When compared with CT, a sonographic finding of severe nephromegaly is 90% sensitive for ALN, whereas nephromegaly with an ill-defined focal mass is 95% sensitive (8). In contrast, a renal abscess would show a central anechoic area with clearly defined margins. Early and accurate identification of lobar nephronia may be crucial. Unlike acute uncomplicated pyelonephritis, outpatient therapy is not effective. Hospital course and fever are often prolonged, and at least 3 weeks of intravenous and oral antibiotic therapy is suggested (4,9). Up to 25% have progressed to renal abscess (5). Identifying ALN is a challenge for emergency physicians. A major barrier is the absence of pyuria in a relatively high percentage of patients (1,6). In the presence of pyuria, the distinction between ALN and uncomplicated pyelonephritis (with their differing management strategies and prognosis) cannot be made without imaging. In the large number of adults seen in EDs with pyuria and flank pain, imaging is seldom performed, and outpatient therapy is the norm. In the absence of pyuria, adults with significant vomiting, fever, and flank or abdominal pain often undergo CT scanning. As in our patient, nonspecific findings of renal inflammation may prompt outpatient antibiotic therapy. This combination of radiographically suggested pyelonephritis and a negative UA should trigger consideration of ALN. Pathophysiologically, the absence of pyuria may reflect localized (‘‘lobar’’) renal parenchymal infection without benefit of drainage via the urinary collecting system (equaling ‘‘early abscess’’). The specific radiologic diagnosis of

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lobar nephronia in our patient was not verified until a postadmission discussion with a body-imaging specialist. A review of the scan with ALN and its implications specifically in mind might have prompted admission of our patient on her first visit. The largest case series of ALN are in children. Algorithms for the identification of serious bacterial infection in immunized infants and children without an obvious source rely heavily on the UA. Pediatric ALN patients without pyuria might well be discharged with a ‘‘viral syndrome’’ diagnosis. Even with pyuria, not all children with a diagnosis of ‘‘febrile urinary tract infection’’ are admitted. Up to 19% of such patients may have ALN (4). Costovertebral angle tenderness may be missed on the physical examination. The fact that up to one-third can be bilateral makes clinically identifying a renal process more difficult (8). Seidel et al. reported on 25 children admitted due to fever with rapid clinical deterioration, and eventually diagnosed with ALN by ultrasound (6). Only 5 of them were initially suspected of having a urinary tract infection, and delay in diagnosis averaged 3 days. Seventy-two percent had pyuria. Earlier consideration of ALN might have prompted more focused antimicrobial therapy (6). CONCLUSION ALN is considered a midpoint in the spectrum of upper urinary tract infections between acute pyelonephritis and intrarenal abscess. A normal UA in patients presenting with fever and abdominal pain may move clinicians to

dismiss a nephrogenic or urologic process. Given that ultrasound was positive in 62–90% of ALN patients, and because the presence of nephromegaly or focal mass is 90–95% sensitive for a CT diagnosis of ALN, ultrasound seems a reasonable screen for ALN, reserving consideration of CT and contrast/radiation exposure for concerning patients with negative ultrasound studies (7,8). Diagnosis may be difficult and inpatient management, sometimes prolonged, is the norm.

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