Pyelonephritis

 

Clinical Manifestations and Symptoms of Pyelonephritis

 

Acute Pyelonephritis

Acute pyelonephritis, especially **obstructive pyelonephritis** (where infection occurs proximal to a urinary tract obstruction), typically presents with a vivid and severe clinical picture. Key symptoms include:

• Fever and Chills: Often high fever (≥38°C or 100.4°F), frequently accompanied by rigors (shaking chills). This is a hallmark symptom.
• Flank Pain (Loin Pain / Back Pain): Pain localized to the costovertebral angle (the area on the back between the lower ribs and the spine) on the affected side. The pain is usually dull and aching but can be severe.
• Lower Urinary Tract Symptoms (LUTS): These may or may not be present but often precede or accompany pyelonephritis if it results from an ascending infection:
  • Dysuria (painful or burning urination)
  • Urinary frequency (needing to urinate more often)
  • Urinary urgency (sudden, strong need to urinate)
• Systemic Symptoms of Intoxication:
  • Nausea and vomiting
  • Malaise, fatigue, and general weakness
  • Loss of appetite
  • Headache
  • Tachycardia (rapid heart rate)
• Costovertebral Angle (CVA) Tenderness: Tenderness elicited by percussion (gentle tapping) over the affected kidney area.

The treatment of patients with acute pyelonephritis, particularly if obstructive or severe, often remains the prerogative of urologists or requires hospital admission for intravenous antibiotics and management of potential complications.

 

Chronic Pyelonephritis

Chronic pyelonephritis, when not in an acute exacerbation phase, often proceeds with very scanty or subtle symptoms. Diagnosis can be challenging as patients may not associate their mild complaints with kidney disease. A targeted questioning of the patient might reveal:

• Episodes of unmotivated low-grade fever (subfebrile condition) or occasional chills.
• Dull, aching pain or discomfort in the lumbar region (flank).
• Nocturia (urination disorders at nighttime, waking up to urinate).
• Decreased work performance, chronic fatigue, and general malaise.
• Loss of appetite or unexplained weight loss.

Often, the only objective sign of chronic pyelonephritis during quiescent periods is an **isolated urinary syndrome** found on routine urinalysis, which may include:

• Leukocyturia (presence of white blood cells in urine, also called pyuria).
• Bacteriuria (presence of bacteria in urine), which may be asymptomatic.
• Proteinuria (protein in urine), typically mild (usually not more than 1 gram per day).

This urinary syndrome might be combined with otherwise unexplained anemia, even in the absence of overt symptoms of renal failure or hypertension.

 

Diagnostics of the Symptoms of Pyelonephritis

Diagnosing pyelonephritis involves a combination of clinical assessment, laboratory tests, and often imaging studies, especially to rule out obstruction or complications.

 

Laboratory Investigations

• Urinalysis:
  • Dipstick Test: May show positive leukocyte esterase (indicating WBCs), nitrites (suggesting presence of nitrate-reducing bacteria like *E. coli*), protein, and blood.
  • Microscopic Examination: Confirms leukocyturia (pyuria), bacteriuria. White blood cell casts, if present, are highly indicative of renal parenchymal infection (pyelonephritis) rather than just lower UTI. Red blood cells (hematuria) may also be seen.
• Urine Culture and Sensitivity: Essential for confirming bacterial infection, identifying the specific pathogen, and determining its susceptibility to various antibiotics to guide targeted therapy. A significant colony count (typically ≥10⁵ colony-forming units/mL in a clean-catch midstream urine sample) is usually indicative of infection.
• Blood Tests:
  • Complete Blood Count (CBC): Often shows leukocytosis (elevated white blood cell count) with a neutrophilic predominance and a "left shift" (increased immature neutrophils) in acute pyelonephritis. Anemia may be present in chronic cases.
  • Inflammatory Markers: Elevated C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) indicate active inflammation.
  • Renal Function Tests: Serum creatinine and blood urea nitrogen (BUN) to assess kidney function. These may be elevated in severe cases or if chronic kidney disease is present.
  • Blood Cultures: Should be performed if the patient is systemically unwell, febrile, or if sepsis is suspected, to detect bacteremia.

To confirm a diagnosis of chronic pyelonephritis, anamnestic data regarding repeated episodes of urinary tract infection or past findings of bacteriuria and leukocyturia (with quantitative assessment) are important. However, the presence of these findings alone does not reliably establish the precise location (level) of the inflammatory process within the urinary tract without further investigation.

Imaging Studies

• Renal Ultrasound: Often the initial imaging modality. It can detect hydronephrosis (suggesting obstruction), kidney size changes, perinephric fluid collections, or large abscesses. It is non-invasive and readily available.
• Intravenous Urography (IVU) or Excretory Urography (IVP): (Less commonly used now due to CT availability). Can reveal decreased tone of the upper urinary tract, caliectasis (dilation of calyces), deformation of calyces, and pyelectasis (dilation of renal pelvis) in chronic pyelonephritis. It can also assess renal function and identify obstructions. Characteristic signs of chronic pyelonephritis include decreased thickness of the renal parenchyma, particularly at the poles of the kidneys (Hodson's symptom), and an increase of more than 0.4 in the renal-cortical index (the ratio of the area of the pyelocaliceal system to the area of the parenchyma).
• Computed Tomography (CT) of the Kidneys: CT scan, especially with intravenous contrast, is highly sensitive and specific for diagnosing pyelonephritis and its complications. It can provide detailed information about the mass and density of the renal parenchyma, the condition of the renal pelvis and calyces, the vascular pedicle, perirenal tissues, and can identify abscesses, obstruction, stones, or gas formation (emphysematous pyelonephritis).
• Voiding Cystourethrography (VCUG): May be indicated, especially in children, to evaluate for vesicoureteral reflux (VUR), which is a significant risk factor for recurrent pyelonephritis.
• Radionuclide Scans (e.g., DMSA scan): Can detect areas of renal scarring (cortical defects) resulting from previous episodes of pyelonephritis and assess differential renal function.

Using ultrasound, kidney size can be specified, and X-ray negative stones (like cystine stones) or intraparenchymal cysts can be detected.

 

Treatment of Pyelonephritis Symptoms

Pyelonephritis is fundamentally an infectious disease. The primary objective of treatment is to eradicate the infection and alleviate the symptoms of the inflammatory process as quickly as possible. This involves achieving high concentrations of appropriate uroseptic (antimicrobial) drugs in the kidney tissue and urinary tract.

 

General Principles and Goals

Treatment goals include:

• Eradication of the causative pathogen.
• Relief of symptoms (fever, pain, LUTS).
• Prevention of complications (e.g., renal abscess, sepsis, chronic kidney disease).
• Identification and correction of any underlying predisposing factors (e.g., obstruction, VUR).

 

Antibiotic Therapy

Prompt initiation of appropriate antibiotic therapy is crucial.

• Empiric Therapy: Since there is a high risk of bacteremia at the onset of pyelonephritis, initial antibiotic therapy is often empiric (started before culture results are available), especially in severe cases or situations precluding rapid urine culture results. Empiric therapy for acute non-obstructive pyelonephritis of severe course typically begins with intravenous administration of antibiotics highly active against common uropathogens, particularly *E. coli*.
  • Drugs of choice often include:
    • Fluoroquinolones (e.g., ciprofloxacin, levofloxacin - use with caution in children).
    • Third-generation cephalosporins (e.g., ceftriaxone, cefotaxime).
    • Aminoglycosides (e.g., gentamicin, amikacin - often in combination, require monitoring for nephrotoxicity and ototoxicity).
    • Aminopenicillins with β-lactamase inhibitors (e.g., ampicillin-sulbactam, amoxicillin-clavulanate).
    • Carbapenems (e.g., meropenem, imipenem-cilastatin) for severe infections or suspected multidrug-resistant organisms.
  • Nitrofurans are rarely used as initial treatment for acute pyelonephritis because, while they achieve high urinary concentrations, their blood and kidney tissue levels may not be sufficient to prevent or treat bacteremia effectively. For similar reasons, aminopenicillins (like ampicillin, amoxicillin) alone or first-generation cephalosporins (cephalexin, cefradine, cefazolin) and nitroxoline are generally not recommended as monotherapy for pyelonephritis due to high rates of resistance among uropathogens and inadequate tissue penetration.
• Targeted Therapy: Once urine culture and sensitivity results are available (usually within 48-72 hours), antibiotic therapy should be tailored to the specific pathogen and its susceptibility profile.
• Duration and Route: Treatment for acute pyelonephritis typically continues for 2-3 days intravenously (or until symptoms of intoxication like fever resolve and urine becomes sterile, as a rule), after which a switch to oral administration of appropriate antibiotics (e.g., cephalosporins, fluoroquinolones, or co-trimoxazole - trimethoprim/sulfamethoxazole) is made. The total duration of therapy for uncomplicated pyelonephritis should not be less than 7-14 days (often 10-14 days). If symptoms of pyelonephritis persist, treatment may need to be continued for up to 6 weeks, and further investigation for complications or underlying issues is warranted.

 

Management of Obstructive Pyelonephritis

If pyelonephritis is associated with urinary tract obstruction (e.g., by a stone or tumor), urgent relief of the obstruction is necessary in addition to antibiotic therapy. This may involve:

• Placement of a ureteral stent.
• Percutaneous nephrostomy tube insertion for kidney drainage.
• Surgical removal or bypassing of the obstruction.

 

Supportive Care

• Hydration: Adequate fluid intake (oral or intravenous) is important to maintain urine flow and help flush bacteria.
• Analgesics and Antipyretics: For pain and fever relief (e.g., acetaminophen, NSAIDs).
• Rest.

 

Differential Diagnosis of Flank Pain and Fever

Symptoms of acute pyelonephritis can mimic other conditions causing flank pain and fever:

Condition	Key Differentiating Features
Acute Pyelonephritis	Flank pain, fever, chills, CVA tenderness, +/- LUTS (dysuria, frequency, urgency). Urinalysis shows pyuria, bacteriuria, +/- WBC casts. Positive urine culture.
Renal Colic due to Urolithiasis	Severe, colicky flank pain radiating to groin; patient restless; hematuria common; nausea/vomiting. Fever/chills suggest concomitant infection (obstructive pyelonephritis). Stone on imaging.
Lobar Pneumonia (Lower Lobe)	Fever, cough, shortness of breath. Pain can sometimes refer to flank/abdomen. Chest X-ray abnormal. No urinary symptoms typically.
Acute Cholecystitis / Biliary Colic	Right upper quadrant or epigastric pain, may radiate to back/right flank. Fever, nausea, vomiting. Murphy's sign. Ultrasound diagnostic.
Acute Appendicitis (especially retrocecal)	Pain often starts periumbilical, then localizes to RLQ but can be atypical. Nausea, vomiting, fever. No primary urinary symptoms usually.
Musculoskeletal Pain (e.g., Paraspinal Muscle Strain)	Pain often related to movement, localized tenderness. No fever or systemic illness. Urinalysis normal.
Herpes Zoster (Shingles)	Unilateral dermatomal pain preceding vesicular rash. Can cause severe flank/back pain. No fever initially unless secondary infection.
Perinephric Abscess	Persistent fever, flank pain, tenderness despite antibiotic treatment for pyelonephritis. Diagnosed by CT/ultrasound showing fluid collection around kidney.

 

Potential Complications of Pyelonephritis

If not treated promptly and effectively, pyelonephritis can lead to serious complications:

• Sepsis and Septic Shock: Life-threatening systemic infection.
• Renal Abscess (Intrarenal or Perinephric): Localized collection of pus within or around the kidney.
• Emphysematous Pyelonephritis: A severe, necrotizing infection characterized by gas formation within the renal parenchyma, more common in diabetic patients. Carries high mortality.
• Papillary Necrosis: Ischemic necrosis of the renal papillae, can lead to obstruction and further kidney damage.
• Chronic Pyelonephritis and Renal Scarring: Recurrent or inadequately treated infections can lead to permanent kidney scarring.
• Chronic Kidney Disease (CKD): Progressive loss of kidney function over time due to repeated damage.
• Hypertension: Can be a consequence of chronic kidney damage.
• Xanthogranulomatous Pyelonephritis: A rare, severe form of chronic pyelonephritis characterized by destructive granulomatous inflammation, often associated with chronic obstruction and infection, sometimes mimicking a renal tumor.

 

Prevention Strategies

Preventing pyelonephritis often involves preventing lower urinary tract infections (cystitis) from ascending, and managing risk factors:

• Treat Lower UTIs Promptly and Adequately.
• Hydration: Drink plenty of fluids.
• Good Personal Hygiene: Wiping front to back for females.
• Urinary Habits: Urinate regularly, completely empty the bladder, urinate after intercourse.
• Management of Predisposing Conditions: Control of diabetes, treatment of BPH or kidney stones, correction of VUR in children if indicated.
• Prophylactic Antibiotics: May be considered for individuals with frequent recurrent UTIs, under medical guidance.

 

When to Seek Medical Attention

Seek immediate medical attention if you experience symptoms suggestive of pyelonephritis, such as:

• Flank, back, or side pain.
• High fever and/or chills.
• Nausea and vomiting.
• Painful or frequent urination.
• Cloudy, dark, bloody, or foul-smelling urine.
• Severe fatigue or malaise.

Prompt diagnosis and treatment are crucial to prevent complications and ensure a full recovery. Hospitalization is often required for severe cases, especially if there are signs of obstruction, sepsis, or if the patient is unable to tolerate oral medications or fluids.