On the terminology of acute kidney infection in adults: Role of the radiologist in its identification and diagnosis by imaging, with emphasis on CT
DOI:
https://doi.org/10.48193/87gdp061Keywords:
Urinary tract infection, Acute pyelonephritis, Computed tomography, Emergency, Imaging, Kidney, PyelonephritisAbstract
Introduction: urinary tract infections (UTIs) are common bacterial infections with heterogeneous clinical phenotypes ranging from benign, uncomplicated infections to complicated UTIs and pyelonephritis, and even severe urosepsis. Imaging in renal infections is complex, given the nature of the findings in most cases. Careful assessment of the clinical situation is essential to accurately select the most informative imaging technique, and therefore, that information must be as precise as possible.
Objective: given the diverse existing nomenclature and the agreement reached by the Society of Uroradiology in 1994, which recommended a simplified nomenclature based on the traditional and widely understood term acute pyelonephritis (APN), our objective is to emphasize and reinforce this nomenclature with current evidence.
Material and methods: a prospective review spanning two years and three months, with clinicopathological correlation, included patients with non-contrast CT (NCCT) and post-contrast CT (PCCT) studies. The analysis examined the terminology used in describing CT findings and their respective reports, emphasizing both the findings described and the final impression.
Results: different and diverse nomenclatures were defined, some of them confusing and lacking a clear context. Pneumonia can manifest as asymmetric perinephric distension or mild renal enlargement in moderate to severe infections. On post-contrast CT (PCCT), pneumonia may appear as wedge-shaped areas of low attenuation with poor corticomedullary differentiation, indicating hypoperfusion and edema. Late-phase images may also show renal sinus obliteration, striated nephrograms, and other findings. More serious complications of pneumonia, such as renal or perinephric abscesses, have been observed.
Conclusions: in our study of patients and their cases, it was identified that a point of agreement should be strengthened and established so that the respective reports, findings, and final impressions adhere to an already accepted and recognized terminology. CT is very sensitive for detecting pyelonephritis and defining its extent, but it is not essential for early, uncomplicated pyelonephritis. Clinical use of CT may be appropriate in cases of persistent fever and leukocytosis that last more than 7 days despite antibiotic treatment.
References
Lee A, Kim HC, Hwang SI, Chin HJ, Na KY, Chae DW, et al. Clinical Usefulness of Unenhanced Computed Tomography in Patients with Acute Pyelonephritis. Journal of Korean Medical Science. 2018;33(38): e236. https://doi.org/10.3346/jkms.2018.33.e236.
Gauthier S, Tattevin P, Soulat L, Bouget J, Abergel S, Hascoet J, et al. Pain intensity and imaging at the initial phase of acute pyelonephritis. Medecine Et Maladies Infectieuses. 2020;50(6): 507–514. https://doi.org/10.1016/j.medmal.2019.07.013.
Ramírez GAM, Arellano E de JO. ¿Dolor abdominal agudo?: La pielonefritis como una posibilidad diagnóstica posibilidad diagnóstica. Anales de Radiología, México. 2006;5(3): 221–229.
Song HK, Shin DH, Na JU, Han SK, Choi PC, Lee JH. Clinical investigation on acute pyelonephritis without pyuria: a retrospective observational study. Journal of Yeungnam Medical Science. 2022;39(1): 39–45. https://doi.org/10.12701/yujm.2021.01207.
Talner LB, Davidson AJ, Lebowitz RL, Dalla Palma L, Goldman SM. Acute pyelonephritis: can we agree on terminology? Radiology. 1994;192(2): 297–305. https://doi.org/10.1148/radiology.192.2.8029384.
Rosenfield AT, Glickman MG, Taylor KJ, Crade M, Hodson J. Acute focal bacterial nephritis (acute lobar nephronia). Radiology. 1979;132(3): 553–561. https://doi.org/10.1148/132.3.553.
Huang JJ, Sung JM, Chen KW, Ruaan MK, Shu GH, Chuang YC. Acute bacterial nephritis: a clinicoradiologic correlation based on computed tomography. The American Journal of Medicine. 1992;93(3): 289–298. https://doi.org/10.1016/0002-9343(92)90235-4.
Kumar PD, Brown LA. Focal bacterial nephritis (lobar nephronia) presenting as renal mass. The American Journal of the Medical Sciences. 2000;320(3): 209–211. https://doi.org/10.1097/00000441-200009000-00013.
Georgiades CS, Moore CJ, Smith DP. Differences of renal parenchymal attenuation for acutely obstructed and unobstructed kidneys on unenhanced helical CT: a useful secondary sign? AJR. American journal of roentgenology. 2001;176(4): 965–968. https://doi.org/10.2214/ajr.176.4.1760965.
Nefropatología. Diagnóstico: Nefronía Lobar. kidneypathology; 2022.
Ifergan J, Pommier R, Brion MC, Glas L, Rocher L, Bellin MF. Imaging in upper urinary tract infections. Diagnostic and Interventional Imaging. 2012;93(6): 509–519. https://doi.org/10.1016/j.diii.2012.03.010.
Zulfiqar M, Ubilla CV, Nicola R, Menias CO. Imaging of Renal Infections and Inflammatory Disease. Radiologic Clinics of North America. 2020;58(5): 909–923. https://doi.org/10.1016/j.rcl.2020.05.004.
Joyce E, Glasner P, Ranganathan S, Swiatecka-Urban A. Tubulointerstitial nephritis: diagnosis, treatment, and monitoring. Pediatric Nephrology. 2017;32(4): 577–587. https://doi.org/10.1007/s00467-016-3394-5.
Nefropatología. Enfermedades tubulointersticiales. kidneypathology; 2022.
Udare A, Abreu-Gomez J, Krishna S, McInnes M, Siegelman E, Schieda N. Imaging Manifestations of Acute and Chronic Renal Infection That Mimics Malignancy: How to Make the Diagnosis Using Computed Tomography and Magnetic Resonance Imaging. Canadian Association of Radiologists Journal = Journal l’Association Canadienne Des Radiologistes. 2019;70(4): 424–433. https://doi.org/10.1016/j.carj.2019.07.002.
Motta Ramírez G A, Bustamante Romero F M, Moreno Aranda J, Alonso Blancas, E, González Merino L. La pielonefritis aguda como origen de afección intraabdominal y simuladora de procesos inflamatorios intraabdominales extrarrenales. Anales de Radiología, México. 2012;11(4): 209–218.
Basmaci I, Sefik E. A novel use of attenuation value (Hounsfield unit) in non-contrast CT: diagnosis of pyonephrosis in obstructed systems. International Urology and Nephrology. 2020;52(1): 9–14. https://doi.org/10.1007/s11255-019-02283-2.
Paick SH, Choo GY, Baek M, Bae SR, Kim HG, Lho YS, et al. Clinical value of acute pyelonephritis grade based on computed tomography in predicting severity and course of acute pyelonephritis. Journal of Computer Assisted Tomography. 2013;37(3): 440–442. https://doi.org/10.1097/RCT.0b013e318287365e.
Kim JS, Lee S, Lee KW, Kim JM, Kim YH, Kim ME. Relationship between uncommon computed tomography findings and clinical aspects in patients with acute pyelonephritis. Korean Journal of Urology. 2014;55(7): 482–486. https://doi.org/10.4111/kju.2014.55.7.482.
Dalla-Palma L, Pozzi-Mucelli R, Pozzi-Mucelli F. Delayed CT in acute renal infection. Seminars in ultrasound, CT, and MR. 1997;18(2): 122–128. https://doi.org/10.1016/s0887-2171(97)90056-1.
Takada T, Yano T, Fujiishi R, Fujii K, Honjo H, Miyajima M, et al. Added value of non-contrast CT for the diagnosis of acute pyelonephritis in older patients with suspected infection with an unknown focus: a retrospective diagnostic study. BMJ open. 2024;14(1): e076678. https://doi.org/10.1136/bmjopen-2023-076678.
Yu TY, Kim HR, Hwang KE, Lee JM, Cho JH, Lee JH. Computed tomography findings associated with bacteremia in adult patients with a urinary tract infection. European Journal of Clinical Microbiology & Infectious Diseases: Official Publication of the European Society of Clinical Microbiology. 2016;35(11): 1883–1887. https://doi.org/10.1007/s10096-016-2743-4.
Hammond NA, Nikolaidis P, Miller FH. Infectious and inflammatory diseases of the kidney. Radiologic Clinics of North America. 2012;50(2): 259–270, vi. https://doi.org/10.1016/j.rcl.2012.02.002.
Leligdowicz A, Dodek PM, Norena M, Wong H, Kumar A, Kumar A, et al. Association between source of infection and hospital mortality in patients who have septic shock. American Journal of Respiratory and Critical Care Medicine. 2014;189(10): 1204–1213. https://doi.org/10.1164/rccm.201310-1875OC.
Piccoli GB, Consiglio V, Deagostini MC, Serra M, Biolcati M, Ragni F, et al. The clinical and imaging presentation of acute ‘non complicated’ pyelonephritis: A new profile for an ancient disease. BMC Nephrology. 2011;12: 68. https://doi.org/10.1186/1471-2369-12-68.
Piccoli GB, Colla L, Burdese M, Marcuccio C, Mezza E, Maass J, et al. Development of kidney scars after acute uncomplicated pyelonephritis: relationship with clinical, laboratory and imaging data at diagnosis. World Journal of Urology. 2006;24(1): 66–73. https://doi.org/10.1007/s00345-005-0044-0.
Kawashima A, Sandler CM, Goldman SM, Raval BK, Fishman EK. CT of renal inflammatory disease. Radiographics: A Review Publication of the Radiological Society of North America, Inc. 1997;17(4): 851–866; discussion 867-868. https://doi.org/10.1148/radiographics.17.4.9225387.
Kawashima A, Sandler CM, Ernst RD, Goldman SM, Raval B, Fishman EK. Renal inflammatory disease: the current role of CT. Critical Reviews in Diagnostic Imaging. 1997;38(5): 369–415.
Taniguchi LS, Torres US, Souza SM, Torres LR, D’Ippolito G. Are the unenhanced and excretory CT phases necessary for the evaluation of acute pyelonephritis? Acta Radiologica. 2017;58(5): 634–640. https://doi.org/10.1177/0284185116665424.
Sarangi P, Bell D, Rasuli B. Perinephric bridging septa. In: Radiopaedia.org. Radiopaedia.org; 2019. https://doi.org/10.53347/rID-65543
Mitreski G, Sutherland T. Radiological diagnosis of perinephric pathology: pictorial essay 2015. Insights into Imaging. 2017;8(1): 155–169. https://doi.org/10.1007/s13244-016-0536-z.
Park D, An C, Yu JS. Association between incidental perirenal fat stranding on CT and metabolic syndrome in otherwise healthy adults. La Radiologia Medica. 2024;129(11): 1587–1596. https://doi.org/10.1007/s11547-024-01888-7.
Fukami H, Takeuchi Y, Kagaya S, Ojima Y, Saito A, Sato H, et al. Perirenal fat stranding is not a powerful diagnostic tool for acute pyelonephritis. International Journal of General Medicine. 2017;10: 137–144. https://doi.org/10.2147/IJGM.S133685.
Tanizaki R, Ichikawa S, Takemura Y. Clinical impact of perinephric fat stranding detected on computed tomography in patients with acute pyelonephritis: a retrospective observational study. European Journal of Clinical Microbiology & Infectious Diseases: Official Publication of the European Society of Clinical Microbiology. 2019;38(11): 2185–2192. https://doi.org/10.1007/s10096-019-03662-4.
Campos-Franco J, Macia C, Huelga E, Diaz-Louzao C, Gude F, Alende R, et al. Acute focal bacterial nephritis in a cohort of hospitalized adult patients with acute pyelonephritis. Assessment of risk factors and a predictive model. European Journal of Internal Medicine. 2017;39: 69–74. https://doi.org/10.1016/j.ejim.2016.12.002.
Lee YJ, Cho S, Kim SR. Unilateral and bilateral acute pyelonephritis: differences in clinical presentation, progress and outcome. Postgraduate Medical Journal. 2014;90(1060): 80–85. https://doi.org/10.1136/postgradmedj-2013-131935.
Yagihashi Y, Shimabukuro S, Toyosato T, Arakaki Y. Can excretory phase computed tomography predict bacteremia in obstructive calculous pyelonephritis? International Urology and Nephrology. 2018;50(12): 2123–2129. https://doi.org/10.1007/s11255-018-1999-2.
Oh SJ, Je BK, Lee SH, Choi WS, Hong D, Kim SB. Comparison of computed tomography findings between bacteremic and non-bacteremic acute pyelonephritis due to Escherichia coli. World Journal of Radiology. 2016;8(4): 403–409. https://doi.org/10.4329/wjr.v8.i4.403.
Sieger N, Kyriazis I, Schaudinn A, Kallidonis P, Neuhaus J, Liatsikos EN, et al. Acute focal bacterial nephritis is associated with invasive diagnostic procedures - a cohort of 138 cases extracted through a systematic review. BMC infectious diseases. 2017;17(1): 240. https://doi.org/10.1186/s12879-017-2336-6.
Park SY. Overuse of Diagnostic Testing in the Management of Korean Patients with Acute Pyelonephritis. Infection & Chemotherapy. 2017;49(1): 84–86. https://doi.org/10.3947/ic.2017.49.1.84.
Jang YR, Ahn SJ, Choi SJ, Eom JS, Cho YK, Shim YS, et al. Clinical and computed tomography factors associated with sepsis in women with clinically uncomplicated pyelonephritis. Abdominal Radiology. 2021;46(2): 723–731. https://doi.org/10.1007/s00261-020-02711-3.
Morgillo M, Bernabei C, Bianchi M, Vezzani V, Mastrodicasa D, Serafini FL, et al. Treatment response assessment of acute pyelonephritis: A multi-reader DWI-based MRI approach. Current Problems in Diagnostic Radiology. 2025;54(2): 197–205. https://doi.org/10.1067/j.cpradiol.2024.07.019.
Lim SK, Ng FC. Acute pyelonephritis and renal abscesses in adults--correlating clinical parameters with radiological (computer tomography) severity. Annals of the Academy of Medicine, Singapore. 2011;40(9): 407–413.
Downloads
Published
Issue
Section
License
Copyright (c) 2026 Revista Mexicana de Urología
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
