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Year : 2017  |  Volume : 31  |  Issue : 1  |  Page : 43-47

Role of emergency ultrasound screening in the management of acute pyelonephritis in emergency department: A large observational study from a tertiary care center of South India

1 Department of Emergency Medicine, Christian Medical College, Vellore, Tamil Nadu, India
2 Department of Biostatistics, Christian Medical College, Vellore, Tamil Nadu, India
3 Department of Radio Diagnosis, Christian Medical College, Vellore, Tamil Nadu, India

Date of Web Publication17-Jan-2017

Correspondence Address:
Kundavaram Paul Prabhakar Abhilash
Department of Emergency Medicine, Christian Medical College, Vellore - 632 004, Tamil Nadu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0972-4958.198461

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Background: Role of emergency ultrasound screening (EUS) in the evaluation of all patients with clinically suspected acute pyelonephritis (APN) in the emergency department (ED) remains unclear. The aim of the study was to describe the frequency of abnormal EUS findings in APN presenting to ED and ascertain the laboratory abnormalities associated with significant abnormal findings to identify the subgroup of patients who will benefit from EUS in ED. Methodology: In this retrospective study, electronic medical records were searched to identify all adult patients who underwent EUS screening from ED for initial clinical diagnosis of APN over 1 year. The EUS findings were categorized into normal, major abnormalities (hydronephrosis, renal abscess, and emphysematous pyelonephritis), and mild abnormalities (cysts, calculi, and renal edema). Results: A total of 1218 patients with initial clinically diagnosed APN underwent EUS. Nearly 49% had a normal EUS while 51% had at least one major or minor abnormality. The frequency of hydroureteronephrosis, renal calculi emphysematous changes, and renal abscess was 19.1%, 8.9%, 2.1%, and 1.9%, respectively. Only 72 (5.9%) patients required emergency percutaneous nephrostomy or drainage of an abscess. Among these patients, EUS was able to identify a major abnormality in sixty (83.3%) patients. Male gender, presence of diabetes mellitus, peripheral white blood cell (WBC) count >10,000 cells/cumm, serum creatinine >1.4 mg%, and urine WBC count >100 cells/hpf were found to independently predict the presence of an abnormality on an EUS. Conclusion: A large proportion of APN patients have only normal or minor abnormalities and do not need additional screening and intervention.

Keywords: Acute pyelonephritis, emergency department, emergency ultrasound, urinary tract infection

How to cite this article:
Mitra S, Acharya H, Dua J, Mutyala SK, Abhilash KP, Yadav B, Shyam Kumar N K. Role of emergency ultrasound screening in the management of acute pyelonephritis in emergency department: A large observational study from a tertiary care center of South India. J Med Soc 2017;31:43-7

How to cite this URL:
Mitra S, Acharya H, Dua J, Mutyala SK, Abhilash KP, Yadav B, Shyam Kumar N K. Role of emergency ultrasound screening in the management of acute pyelonephritis in emergency department: A large observational study from a tertiary care center of South India. J Med Soc [serial online] 2017 [cited 2022 May 19];31:43-7. Available from:

  Introduction Top

Acute pyelonephritis (APN) is one of the most common reasons for emergency department (ED) admission and accounts for considerable morbidity and health-care costs. [1],[2] In most cases, the diagnosis of urinary tract infection (UTI) can be made on clinical grounds and by demonstration of leukocyturia. [3] Several imaging modalities to aid in the evaluation of patients with APN exist. Computed tomography (CT) of the kidneys probably yield the maximum information, but its routine use is hindered by the risk of radiation exposure and allergic reactions and nephrotoxic risks due to contrast. [3],[4] Emergency ultrasound screening (EUS) is quite often used as an adjunct investigation to look for the complications of APN. [5],[6],[7],[8] Ultrasonography offers the advantage of no radiation exposure and no requirement of contrast, but it is limited in the evaluation of renal function and by the fact that it is highly operator dependent. The Infectious Disease Society of America and European Association of Urology recommend ultrasound evaluation to rule out urinary obstruction if fever persists after 72 h of appropriate treatment. [9],[10] A few prospective studies have suggested clinical rules to predict the need for radiologic imaging in febrile UTI patients in the ED. [6],[7],[8],[11] The presence of septic shock, elevated procalcitonin level, C-reactive protein, renal dysfunction, or patients with either a history of nephrolithiasis or renal insufficiency may benefit from ultrasound screening. [12] Despite these recommendations, EUS is done in a large proportion of patients presenting with APN to the ED. Therefore, we conducted this large retrospective study with the aim of describing the rate of sonological abnormalities and assessing the utility of EUS in determining the need for surgical intervention.

  Methodology Top

This retrospective observational study was done in the adult ED and the Department of Radio Diagnosis at a tertiary care teaching hospital in Vellore, South India, which is a 2700-bedded tertiary care teaching hospital in South India. The adult ED is a 45-bedded unit which admits 190-220 patients per day.

All adult patients (age ≥16 years) who underwent EUS in the ED for clinically suspected APN between January 1, 2014, and December 31, 2014, were included in the study. The electronic medical records were searched using key words such as "pyelonephritis," "APN," "UTI," and "cystitis." Patients with known urogenital structural abnormalities were excluded from our study. The data on demographic details, clinical findings (including the comorbidities, radiological, and biochemical), and microbiological results were obtained from the Computerized Hospital Information Processing system on the predesigned clinical research pro forma.

According to our ED protocol, all patients with fever, flank tenderness, and leukocyturia would be screened by EUS for complications. CT imaging of the kidneys was then done for patients with suspected emphysematous pyelonephritis. The EUS is performed by trained radiologists in the Department of Radio Diagnosis of our hospital. The EUS findings were recorded and were classified as normal and abnormal. The severity of the EUS findings was graded as major or minor as defined below:

  • Major abnormality: Hydroureteronephrosis, renal abscess, and emphysematous pyelonephritis
  • Minor abnormality: Renal cysts, renal stones, swelling, and perinephric stranding.

We also conducted a subgroup analysis of EUS abnormalities among patients who had a culture-confirmed (urine and/or blood) APN.

Statistical analysis

The data were then transferred to the Microsoft Excel (version 16) and analyzed using Statistical Package for Social Sciences for Windows (SPSS Inc., Released 2007, version 16.0, Chicago, IL, USA). For comparison between the groups, continuous variables are presented as mean (standard deviation) or as median (range) depending on the distribution of the data. Categorical and nominal variables are presented as percentages. Chi-square test or Fisher's exact test was used to compare dichotomous variables, and t-test or Mann-Whitney test was used for continuous variables as appropriate. The differences between the two groups were analyzed by univariate and multivariate logistic regression analyses and their 95% confidence intervals were calculated. For all tests, a two-sided P < 0.05 was considered statistically significant.

This study was approved by the Institutional Review Board (IRB Min. No. 9243 dated January 12, 2015), and patient confidentiality was maintained using unique identifiers and by password-protected data entry software with restricted users.

  Results Top

The study included 1218 patients, who underwent EUS between January 01, 2014, and December 31, 2014, in our ED after a clinical diagnosis of APN was made. There was a slight female predominance (53.4%). The median age was 54 years (range: 16-90 years). Leukocytosis was evident in 836 patients (68.6%). The baseline characteristics are shown in [Table 1].
Table 1: Baseline characteristics (n=1218)

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Out of the 1218 patients, 597 (49%) had normal findings on EUS while 621 (51%) had at least one major or minor abnormal finding. Some patients had more than one major abnormality on the EUS. The frequency of major abnormal findings such as hydroureteronephrosis, emphysematous changes, and renal abscess was 19.1%, 2.1%, and1.9%, respectively [Table 2].
Table 2: Distribution of the emergency ultrasound screening findings

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Additional CT imaging was performed in 180 (14.8%) patients. The rate of major abnormalities detected on CT imaging in these patients was as follows: hydronephrosis (69/180; 38.3%), renal abscess (5/180; 2.8%), and emphysematous pyelonephritis (13/180; 7.2%). Minor abnormalities such as renal cyst, renal stone, peri-nephric stranding, and bulky/swollen kidneys were seen in 10 (5.5%), 33 (18.3%), 91 (50.5%), and 46 (25.5%) patients, respectively. Overall, the percentage of major abnormalities detected by EUS was 20.2% (248/1218 patients) and by CT imaging was 45.5% (82/180 patients).

Urine culture was performed on 980 (80.5%) cases. A significant growth of uropathogens was seen in 645 (65.8%) patients, while 335 (34.2%) cultures remained sterile or had insignificant growth. Common organisms included Escherichia coli (41.8%), Klebsiella spp (3.8%), Enterococcus (5.8%), Pseudomonas (1.6%), Proteus (1.1%), Citrobacter species (1%), and others. We compared the occurrence of EUS abnormalities among the urine culture-confirmed cases of APN [Table 3]. EUS was normal in 47.1% of patients with culture-positive APN and in 45.4% of patients with culture-negative APN.
Table 3: Comparison of emergency ultrasound screening findings with culture result

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Surgical intervention in the form of percutaneous nephrostomy or drainage of abscess was required in 72 (5.9%) patients. Among these patients, EUS was able to identify a major abnormality in sixty (83.3%) patients. Among those who required surgical intervention, additional CT imaging was performed in 36 (55.4%) patients after the initial EUS.

The variables that were significantly associated with an abnormal EUS finding were included in the multivariate logistic regression analysis. Male gender, presence of diabetes mellitus, peripheral white blood cell (WBC) count >10,000 cells/cumm, serum creatinine >1.4 mg%, and urine WBC count >100 cells/hpf were found to independently predict the presence of an abnormality on a EUS [Table 4].
Table 4: Univariate and multivariate analysis of the variables among normal and abnormal emergency ultrasound screening findings

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  Discussion Top

The diagnosis of APN is largely based on clinical features (fever, dysuria, hematuria, and costovertebral angle tenderness) and demonstration of pyuria on urine analysis. [3] Complicated APN such as obstructive uropathy, renal abscess, and emphysematous pyelonephritis, if untreated, can result in septic shock and death. [1],[12] Hence, it is essential to identify these abnormalities in the ED so that prompt surgical intervention may be done. EUS and CT abdomen are the two commonly used radiological imaging techniques to detect these complications. Though these imaging tests are widely available in many EDs, overutilization of resources and workforce without any added benefit to patient care remains a concern. Hence, we evaluated the utility of EUS in the management of APN in our ED.

The detection of abnormalities on a EUS ranges from 42.5% to 63.5% as seen in different studies. [5],[6],[7],[8] Our study showed abnormalities on EUS in 51% of patients. The detection rate of major abnormalities in our study (20.2%) was lesser than that reported by Chen et al. [6] However, the detection rate of major abnormalities on CT imaging of 45.5% was similar to the detection rates in other studies. [4] This ascertains the fact that EUS is a very easy, important, and noninvasive tool that is increasingly used in EDs across the world for the early detection of abnormalities.

As per the American College of Radiology guidelines, routine radiological imaging (X-ray pyelography, EUS, CT, or magnetic resonance imaging) has a limited role and adds little to the management of patients with acute uncomplicated APN if the patient responds to therapy within 72 h. [13] We, therefore, tried to identify the factors predicting abnormalities on a EUS so that indiscriminate use of EUS can be avoided. We found the presence of diabetes mellitus, peripheral WBC count >10,000 cells/cumm, serum creatinine >1.4 mg%, and urine WBC count >100 cells/hpf to be associated with abnormal ultrasound findings. Neal et al. reported diabetes mellitus to be the only factor associated with the presence of an abnormal ultrasound finding among patients with APN. [5] Rollino et al. found no significant correlation between leukocytosis, ESR, CRP, urinary leukocytes, urine culture, and duration of symptoms between patients with positive and negative CT scans. [14],[15]

Surgical interventions that are usually required in cases of complicated APN include percutaneous nephrostomy, abscess aspiration, ureteroscopic stone manipulation, lithotripsy, or nephrectomy. Although more than half of our patients had an abnormal finding on EUS, only 5.9% of the patients required surgical intervention. In 1997, Luján Galán et al. reported that only 42.5% of patients with APN had an abnormal EUS and only 5.8% required surgical intervention. [8] Neal et al. reported a 11.2% rate of surgical intervention among patients who had a EUS for APN. [5] A meta-analysis by García-Ferrer et al. also showed that EUS resulted in surgical intervention in only 11.5% of patients with APN. [7] Hence, the routine use of ultrasound screening in all cases of suspected APN is not justifiable. Most EDs have constraints in workforce, time, and availability of trained radiologists and hence, overusage of a low yield test in all cases of APN makes it a futile exercise. Hence, only patients with a high risk of developing a complicated APN should be screened so that appropriate surgical intervention may be initiated.

Our study has certain limitations. As it was conducted at a single medical center, the patient population may be biased by patient selection and referral pattern. Since this study was a retrospective survey, some data were missing and we did not have any control over the radiographic evaluation of all adult patients with suspected APN. Nonetheless, the study provides relatively rare information about the utility of EUS among patients with suspected APN.

  Conclusion Top

A large proportion of APN patients (clinically diagnosed as well as microbiologically confirmed cases) may have a normal or minor abnormality and do not need additional intervention. The fact that EUS detected abnormalities in 51% of patients ascertains its importance as an easy, noninvasive screening tool in the ED. However, its routine and indiscriminate use for all clinically suspected or culture-confirmed cases of APN in ED may lead to overutilization of resources without any added advantage to patient management. Abnormal EUS findings may be suspected in patients with diabetes, patients with higher peripheral or urine WBC counts, and those with renal failure.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Foxman B, Klemstine KL, Brown PD. Acute pyelonephritis in US hospitals in 1997: Hospitalization and in-hospital mortality. Ann Epidemiol 2003;13:144-50.  Back to cited text no. 1
Sammon JD, Sharma P, Rahbar H, Roghmann F, Ghani KR, Sukumar S, et al. Predictors of admission in patients presenting to the emergency department with urinary tract infection. World J Urol 2014;32:813-9.  Back to cited text no. 2
Ramakrishnan K, Scheid DC. Diagnosis and management of acute pyelonephritis in adults. Am Fam Physician 2005;71:933-42.  Back to cited text no. 3
Lim SK, Ng FC. Acute pyelonephritis and renal abscesses in adults - Correlating clinical parameters with radiological (computer tomography) severity. Ann Acad Med Singapore 2011;40:407-13.  Back to cited text no. 4
Neal DE Jr., Steele R, Sloane B. Ultrasonography in the differentiation of complicated and uncomplicated acute pyelonephritis. Am J Kidney Dis 1990;16:478-80.  Back to cited text no. 5
Chen KC, Hung SW, Seow VK, Chong CF, Wang TL, Li YC, et al. The role of emergency ultrasound for evaluating acute pyelonephritis in the ED. Am J Emerg Med 2011;29:721-4.  Back to cited text no. 6
García-Ferrer L, Primo J, Juan Escudero JU, Ordoño Domínguez F, Esteban JM. The use of renal ultrasound for adult acute pyelonephritis. Arch Esp Urol 2007;60:519-24.  Back to cited text no. 7
Luján Galán M, Páez Borda A, Fernández González I, Llorente Abarca C, Romero Cajigal I, Bustamante Alarma S, et al. Usefulness of ultrasonography in the assessment of acute pyelonephritis. Arch Esp Urol 1997;50:46-50.  Back to cited text no. 8
Gupta K, Hooton TM, Naber KG, Wullt B, Colgan R, Miller LG, et al. International clinical practice guidelines for the treatment of acute uncomplicated cystitis and pyelonephritis in women: A 2010 update by the Infectious Diseases Society of America and the European Society for Microbiology and Infectious Diseases. Clin Infect Dis 2011;52:e103-20.  Back to cited text no. 9
van Nieuwkoop C, Hoppe BP, Bonten TN, Van't Wout JW, Aarts NJ, Mertens BJ, et al. Predicting the need for radiologic imaging in adults with febrile urinary tract infection. Clin Infect Dis 2010;51:1266-72.  Back to cited text no. 10
Xu RY, Liu HW, Liu JL, Dong JH. Procalcitonin and C-reactive protein in urinary tract infection diagnosis. BMC Urol 2014;14:45.  Back to cited text no. 11
Efstathiou SP, Pefanis AV, Tsioulos DI, Zacharos ID, Tsiakou AG, Mitromaras AG, et al. Acute pyelonephritis in adults: Prediction of mortality and failure of treatment. Arch Intern Med 2003;163:1206-12.  Back to cited text no. 12
Sandler CM, Amis ES Jr., Bigongiari LR, Bluth EI, Bush WH Jr., Choyke PL, et al. Imaging in acute pyelonephritis. American College of Radiology. ACR Appropriateness Criteria. Radiology 2000;215 Suppl:677-81.  Back to cited text no. 13
Rollino C, Boero R, Ferro M, Anglesio A, Vaudano GP, Cametti A, et al. Acute pyelonephritis: Analysis of 52 cases. Ren Fail 2002;24:601-8.  Back to cited text no. 14
Rollino C, Beltrame G, Ferro M, Quattrocchio G, Sandrone M, Quarello F. Acute pyelonephritis in adults: A case series of 223 patients. Nephrol Dial Transplant 2012;27:3488-93.  Back to cited text no. 15


  [Table 1], [Table 2], [Table 3], [Table 4]

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