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Year : 2017  |  Volume : 15  |  Issue : 3  |  Page : 245-246

An airy phenomenon

Department of Nephrology, Christian Medical College, Vellore, Tamil Nadu, India

Date of Web Publication7-Aug-2017

Correspondence Address:
Anna Valson
Department of Nephrology, Christian Medical College, Vellore - 632 004, Tamil Nadu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/cmi.cmi_50_17

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How to cite this article:
Valson A. An airy phenomenon. Curr Med Issues 2017;15:245-6

How to cite this URL:
Valson A. An airy phenomenon. Curr Med Issues [serial online] 2017 [cited 2023 Jun 9];15:245-6. Available from: https://www.cmijournal.org/text.asp?2017/15/3/245/212373

  Introduction Top

A 45-year-old female who had been diabetic for the last 5years with a history of poor glycemic control, presented with high grade fever with chills, severe noncolicky nonradiating left flank pain, dysuria, vomiting and decreased urine output for 4days. There was no haematuria or calculuria(passage of stones in the urine). On examination, she was found to have a blood pressure of 100/60 mmHg, pulse rate of 100/min and left renal angle tenderness. All other systems were unremarkable. Laboratory tests revealed an glycated hemoglobin(HbA1C) of 10.3%, serum creatinine 4.5mg/dL, haemoglobin 7.6g/dL, white blood cell count 25,300/mm [3], platelet count 1 lakh/mm [3]. Urine showed numerous pus cells/high power field(HPF), 40–50 red blood cells/HPF, sugar 3+, ketones negative. Ultrasound and noncontrast computed tomography(CT) of the kidney-ureter-bladder(KUB) are shown in [Figure1] and [Figure 2].
Figure1: Ultrasound kidney-ureter-bladder of the patient.

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Figure2: Noncontrast computed tomography kidney-ureter-bladder of the patient.

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  Questions Top

  1. Describe the findings on the ultrasound KUB and CT KUB
  2. What are the common predisposing factors for this condition?
  3. What is its pathophysiology?
  4. How is this condition classified, based on radiological appearance?
  5. How is this condition managed?

  Answers Top

  1. The ultrasound KUB of the left kidney shows “dirty” distal acoustic shadowing(white arrow) caused by intrarenal air pockets, that are seen as echogenic foci(blue arrow).(This is in contrast to the 'clean' or echo free shadowing caused by kidney stones). CT KUB shows an enlarged left kidney with presence of intraparenchymal air in the anterior and lateral cortex and extension of air into the perinephric space(indicated by an arrow). This condition, in which a necrotizing infection of the renal parenchyma produces intrarenal suppuration and gas formation, is called emphysematous pyelonephritis(EPN)
  2. Diabetes, especially diabetes with poor glycemic control(HbA1C>8%) is the most important risk factor for EPN, accounting for 85%–96% of cases. Other risk factors include urinary tract obstruction, renal calculi, polycystic kidney disease, female gender(75% cases occur in females, who are in general, more prone to urinary tract infection), and immunocompromised patients such as renal transplant recipients [1],[2]
  3. EPN is caused by pathogenic gas forming bacteria such as Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis and Pseudomonas aeruginosa which are capable of mixed acid fermentation. In immunocompromised hosts (as for example, this lady with long standing, poorly managed diabetes), these organisms are able to multiply prolifically, and in a hyperglycemic environment(seen in diabetes) fermentation of glucose produces carbon dioxide and hydrogen gas. Due to impaired microcirculation secondary to inflammation, microangiopathy or urinary tract obstruction, gas, which would have normally been reabsorbed by the renal vasculature, accumulates.[3] The left kidney is more commonly involved than the right(52%), and only 10% cases are bilateral [1]
  4. Based on CT findings, EPN is classified as follows:[3] Class1–when gas is present in the collecting system of the kidney alone, Class2–when gas is present in the renal parenchyma but does not extend into the extrarenal space, Class3a–extension of gas into the perinephric space, Class3b–extension of gas into the pararenal space, Class4–bilateral EPN or EPN in a solitary kidney. This patient had Class3a EPN. Further, there are two types of EPN described, which have prognostic relevance.[4] Type1 EPN has predominantly renal necrosis(>1/3 of renal parenchyma) with absence of intrarenal or perinephric fluid collections on CT and presence of streaky/mottled gas shadows, and is also called “dry EPN.” This is less common, but has a higher mortality and a more fulminant course. Type2 EPN, also called “wet EPN,” is characterized by renal or perinephric fluid collection with bubbly or loculated gas shadows in the parenchyma or collecting system, as was seen in this patient. It has a better prognosis
  5. Risk factors for poor outcome in patients with EPN include Type1 EPN, Class3 and 4 EPN, thrombocytopenia, elevated serum creatinine(>1.4mg/dL), shock and altered sensorium.[3],[4] The three treatment modalities available include IV antibiotics alone, IV antibiotics with percutaneous drainage(PCD) and in refractory cases, nephrectomy. Mortality is least for patients undergoing PCD, which is now part of first line treatment for EPN.[1],[2] Nephrectomy is reserved for patients with extensive or fulminating disease, or those not responding to antibiotics and PCD. This patient received broad spectrum antibiotics and PCD and renal function reached a nadir of 1.3mg/dL after treatment.

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There are no conflicts of interest.

  References Top

AboumarzoukOM, HughesO, NarahariK, CoulthardR, KynastonH, ChlostaP, etal. Emphysematous pyelonephritis: Time for a management plan with an evidence-based approach. Arab J Urol 2014;12:106-15.  Back to cited text no. 1
SomaniBK, NabiG, ThorpeP, HusseyJ, CookJ, N'Dow J; ABACUS Research Group. Is percutaneous drainage the new gold standard in the management of emphysematous pyelonephritis? Evidence from a systematic review. JUrol 2008;179:1844-9.  Back to cited text no. 2
HuangJJ, TsengCC. Emphysematous pyelonephritis: Clinicoradiological classification, management, prognosis, and pathogenesis. Arch Intern Med 2000;160:797-805.  Back to cited text no. 3
WanYL, LoSK, BullardMJ, ChangPL, LeeTY. Predictors of outcome in emphysematous pyelonephritis. JUrol 1998;159:369-73.  Back to cited text no. 4


  [Figure 1], [Figure 2]


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