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Acute and chronic pyelonephritis

Updated on March 30, 2013

Acute pyelonephritis

Chronic pyelonephritis

Acute pyelonephritis

Acute pyelonephritis is one of the commonest subtype of tubulointestitial renal diseases. There is acute inflammation in the renal tubules and the interstitium due to an infectious cause. The infection settles in the renal parenchyma leading to acute inflammation with neutrophils and edema in the interstitium. Then the neutrophils invade the renal tubules causing tubulitis, renal tubular destruction and formation of microabscesses in the renal parenchyma. Next the infection spreads through the entire renal parenchyma, usually sparing the glomeruli.

Macroscopic appearance of acute pyelonephritis:
Surface of the kidney is dull and opaque. Small multiple subcapsular abscesses may be seen. Cut surface of the kidney shows multiple small abscesses or streaks of pus in the renal cortex. Features of complications may or may not be present.

Microscopic appearance of acute pyelonephritis:
Edema and neutrophil infiltration of the interstitium can be seen under the light microscope. Also there is tubulitis, microabscesses formation and pus cell casts in the renal tubules.

Complications of acute pyelonephritis:

  • Renal papillary necrosis.
  • Pyonephrosis - accumulation of purulent exudate in the kidney. This is usually due to associated complete or almost complete obstruction in the pelvis/ureters preventing drainage of the exudate.
  • Perinephric abscesses – extension of suppurative exudate through the renal capsule into the perinephric tissue.

In most patients, acute pyelonephritis follows an uncomplicated course with treatment. However, patients with obstruction, diabetes mellitus and immunodeficiency can have complications.

Clinical features:

  • Fever (usually high fever with chills and rigors).
  • Dysuria.
  • Hematuria.
  • Pain in the costovertibral angle on the affected side.


Presence of pus cell casts in urine analysis will show renal involvement. In lower urinary tract involvement there is only pus cells, no casts.

Chronic pyelonephritis

Chronic pyelonephritis is characterized by chronic inflammatory infiltration of the interstitium, interstitial scarring and tubular atrophy. In advanced cases there is glomerular sclerosis secondary to severe tubular involvement. Chronic pyelonephritis frequently progresses into end stage renal failure.

Chronic pyelonephritis could be due to two main causes:

  1. Reflux nephropathy - associated with chronic vesicoureteric reflux and intrarenal reflux. Recurrent acute pyelonephritis lead to chronic pyelonephritis eventually.
  2. Chronic obstructive pyelonephritis - obstruction in the renal tract (e.g, calculi, posterior urethral valves) predisposes to infection. Here too recurrent acute pyelonephritis lead to chronic pyelonephritis.

Macroscopic appearance:
Affected kidney is smaller in size (contracted) and the surface shows coarse scarring. If both kidneys are affected appearance is asymmetrical. Cut sections of the kidney show calyces are deformed and blunted. Coarse scarring involving the corticomedullary regions, and more prominent in upper and lower poles (if reflux associated). In obstruction associated cases there could be features of hydronephrosis too. (Compare the macroscopic features of chronic pyelonephritis with chronic glomerulonephritis)

Microscopy of chronic pyelonephritis:
Interstitium will show chronic inflammatory infilatration and fibrosis.There will be renal tubular atrophy with accumulation of secretions giving rise to thyroid like appearance – thyroidization.
The glomeruli are relatively spared. But there can be periglomerular sclerosis and in advanced cases glomerular sclerosis. The blood vessels usually show hypertension associated vascular changes (hyaline arteriolosclerosis).

Clinical features:
Usually the patients are asymptomatic and patient may eventually present with features of end stage renal disease such as frothy urine, oliguria or anuria, generalized edema, fatiguability and uremic symptoms. Asymptomatic patients may also be picked by when investigating for hypertension, presence of proteinuria in routine urine examinations. But the patient could show episodes of features of acute pyelonephritis.

Xanthogranulomatous pyelonephritis
A type of chronic pyelonephritis characterized by presence of a chronic inflammatory infiltration with numerous foamy macrophages. Macroscopically they can form a tumor like mass mimicking renal cell carcinoma. Xanthogranulomatous pyelonephritis is associated with diabetes mellitus and obstruction related infections caused by proteus.

Toxic tubulointerstitial nephritis /nephropathy
Usually the appearance is nonspecific inflammation and fibrosis in the interstitium with tubular changes. Severe cases may even look like chronic pyelonephritis. Some cases may have interstitial fibrosis without significant inflammation. Toxins could be drugs or heavy metals.

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      Johana 2 years ago

      there was nothing more she could do for me.. I have tried a mttiuulde of meds: specifice to migrain Imetrex, Midrin, Elavil, Amaryl, DHE, Tramadol,and recently had BOTOX inject that was pointless and expessive! I have had narcotic combos: I give myself IM. To no avail. The DHE nasal spray did nothing but when hospitalized and DHE was given IV it seemed to give temporary relief. I have also used Torodol IM and Po ..no change. I have used a concoction of Demerol 200mg Im w/ Benadry 50mgIM and Phenergan 25mg IM. That did absolutely NOTHING. I am at a loss. I have changed my diet and eliminated all foods that are triggers and that did nothing. I am at the end of my rope. I can no longer work as a critical care RN or any other job because I cannot count on a day void of the migraine. Florescent lighting, noise, and strong odors/fragrences are my uncontrollable triggers as it relates to employment. I have seen numerous neurologist had multiple tests: EEG, CT w/wo contrast, nerve blocks, and the tests only show an abnormality on the L side of my brain but no one seem to be able to address this or knows what or how to take care of it. My headaches start in my occipital region causing stiff neck then progresses to the left temporal (I have a constant ringing in my ear and my Otolaryngologist started me on Polyfavinoid(?)then proceeds to the frontal. All of my pain seems to be on the L-side to the frontal. As it progresses the L side of my face becomes numb and my vision doubles. I don't know if that is considered and Aura. Presently the only med. I am on is Ameryl25mg BID. I have nothing for the excrutiating pain. I have nausea and occassionally vomiting. I might tell you at this point, that I do have an underlying condition Mixed Connective Tissue Disease. Which has a profound effect on any therapy I try. I get one thing under control and then another issue goes out of control. Presently I have a DCPM for Neurocardiogenic Syncope, profound brady 20bpm-30bpm. and VT, I continue to have syncopal episodes even with the pacemaker and its built-in controlls for my NeuroCardioGenic sycope. I have a respiratory issue w/ a new diagnosis of Reactive Airway Disease and Asthma (I can not tolerate cold or odors), I have a Rheumatologist, who has been helpful (in her field but not w/ the migraines). The Neurologist I had recently advised me there was nothing further she could do for me and sent me back to my primary MD who specializes in Internal Medicine and Renal ( I have had episodes of ARF and stones -hospitalized for both issues surgery for the stones). I have had multiple hospitalizations and right now I do not know where to go. I have had 2 GI bleeds requiring intervention D/T medications.I would like to see you at the Mayo Clinic in Arizona (as my husband and I are thinking to moving to a warmer climate for me)since many of my issues are triggered my changes in temp. We are looking at a time in April and are willing to fly out and take a chance on anything you might be able to offer.) I must say one thing, I have had doctors that I have seen one time and then theyturn me over to their Resident I do not want that to be the case if I make this trip to see you. I hape you can understand. I can bring all of my records from all MDs. and hospital stays, tests, etc. Please advise me if you would be willing to see me. I have done much research as has my husband and what you are doing w/ migraine control looks promising. Please let me know if you can take on my request. I look forward to hearing from you in the near future.Sincerely,Juanita (Anita) Starika