Acute pyelonephritis: clinical presentation and examination
The acute form of the disease proceeds as an exudative inflammation and rapidly leads to impaired function of the affected organ. The clinical picture is pronounced and consists of two complexes.
- General intoxication: the patient suffers from high fever (often of a hectic type), debilitating profuse sweating, and shaking chills.
- Local manifestations: tension of the abdominal wall and lumbar muscles is noted. A key physical sign is sharp tenderness upon bimanual (bilateral) kidney palpation.
In laboratory diagnostics, urine changes appear sequentially: bacteriuria is recorded first, and only then is the excretion of leukocytes (pyuria) added. The blood reacts with typical inflammatory shifts: ESR increases, the number of leukocytes increases with the appearance of young and band forms, and toxic granularity of neutrophils is determined. Chromocystoscopy, plain radiography, and excretory urography are used to assess the anatomical state.
Development and symptoms of chronic pyelonephritis
The chronic process is characterized by progressive inflammation. Most of the time, this is a consequence of an undertreated acute phase, whereas primary chronic variants are rare. The course can be latent or recurrent.
An early sign, often preceding other symptoms, is arterial hypertension. It occurs in parallel with the first shifts in urine tests. Due to the concealed course, the pathology is often detected late, when the patient has already developed chronic kidney disease (CKD).
The pathophysiological mechanism of the late stages includes:
- A drop in the glomerular filtration rate and a decrease in renal blood flow.
- Loss of the urine-concentrating function of the kidneys, which leads to frequent nighttime urination (nocturia) and an increase in daily urine volume (polyuria).
- Tubular dysfunction, which often proceeds with the development of hyperchloremic acidosis.
At the CKD stage, general weakness, weight loss, anorexia, and nausea join the picture.
Laboratory markers of chronic inflammation
The diagnostics of the chronic form have a number of pitfalls. The main feature is that bacteriuria and leukocyturia appear episodically. A negative test result does not rule out the diagnosis — the study must be repeated multiple times. Leukocyturia is assessed by daily cell excretion, which is crucial for confirming the diagnosis. Proteinuria is present, but is moderate in nature and never exceeds 2 g/day.
Intravenous urography in the early stages may not show abnormalities. However, as it progresses, contour irregularity, a decrease in kidney size, and persistent deformation and dilation of the pelvicalyceal system are visualized. The prognosis of the disease is a slow but steady development of CKD. The only significant factor capable of slowing down organ degradation is the timely restoration of normal urine outflow.
Briefly: answers to topical questions
Which bacteria are most often the causative agents of pyelonephritis?
The main etiological agent of pyelonephritis is Gram-negative microflora. Among the main pathogens in hematogenous or lymphogenous pathways are indicated:
- Escherichia coli (E. coli);
- Klebsiella;
- Enterococci;
- Proteus.
For gestational pyelonephritis, representatives of the intestinal group are most frequently indicated: Escherichia coli, Proteus, Klebsiella, Streptococcus. In acute pyelonephritis, monoinfection predominates; in a prolonged course, mixed infection.
What instrumental methods are used to diagnose acute pyelonephritis?
For the diagnosis of acute pyelonephritis, the manual indicates the following instrumental methods:
- plain radiography of the urinary system;
- excretory urography;
- chromocystoscopy.
In pregnant patients with a diagnosed "acute pyelonephritis", an obligatory instrumental method is renal ultrasound. In the absence of positive clinical and laboratory dynamics 48–72 hours after the start of treatment, a repeated renal ultrasound and, if possible, renal MRI are performed to identify complicating factors and clarify the anatomical and functional state of the kidneys.
With which diseases is differential diagnosis of acute pyelonephritis carried out?
According to the sources, acute pyelonephritis is compared with conditions having similar pain manifestations:
- acute nephritis — usually bilateral dull pains;
- renal infarction — like acute pyelonephritis, can manifest with sharp, often unilateral pains;
- nephroptosis — associated with excessive kidney mobility, impaired hemo- and urodynamics, triggered by sudden movements;
- acute paranephritis — severe constant pain, increasing when trying to straighten the leg on the affected side.
Differential diagnosis is also carried out with secondary non-infectious interstitial nephritis: pyelonephritis is characterized by bacterial infection, pyuria, bacteriuria, and deformations of the renal pelves; secondary interstitial nephritis is characterized by systemic or medicinal causes, early polyuria, proteinuria, microhematuria, cylindruria, rare bacteriuria, and the absence of pelvic changes characteristic of pyelonephritis.
In pregnant women, differential diagnosis with acute appendicitis is separately given in the materials: with appendicitis, pain appears first, then body temperature rises and vomiting occurs; with pyelonephritis, the disease begins with chills, vomiting, and fever, then pain in the lumbar region and a positive Pasternatsky symptom appear. The main differential diagnostic criterion for pyelonephritis is changes in the urine test: leukocyturia and hematuria.
The triad of acute pyelonephritis is FBP: Fever, Back pain, Pyuria.
Class and exam questions
Why is a single good urine test not enough when chronic pyelonephritis is suspected?
Because leukocytes and bacteria are excreted episodically during a chronic course. To exclude or confirm the diagnosis, tests must be retaken.
Which symptom often appears first in chronic pyelonephritis?
Arterial hypertension. It can occur before the appearance of typical renal complaints, simultaneously with initial changes in the urine.
What precedes the appearance of pus in the urine in the acute form?
Bacteriuria always appears first, and only then is clinically significant leukocyturia (pyuria) added.
What is the most important condition for slowing down chronic pyelonephritis?
The key factor in slowing down the destruction of renal tissue is the complete restoration of adequate urine outflow.
What else to study on this topic
- Two main pathways of bacterial infection penetration into the kidney
- Mechanism of development of vesicoureteral reflux
- Technique of bimanual kidney palpation
- Differential diagnosis of types of fever in intoxication syndrome
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