Infections and Pathology of the Urinary Tract Flashcards
Introduction
Bacterial infections common in young and
middle-aged females
• Occurs in infant males and elderly men if there
is an underlying UT abnormality
• Aetiologic organisms is usually a gram neg
bacterium, often a faecal contaminant from the
perineum, such as E. coli or Klebsiella
• Basic sequence starts as a cystitis, with or
without vesico-ureteral reflux, followed by
ureteritis and acute pyelonephritis, and possibly
then chronic pyelonephritis
Cystitis:
Introduction/Definition
Cystitis • Inflammation of the urinary bladder, mostly due to bacterial infection • Commonly seen in girls and young women owing to the shorter urethra, as compared to males • Cystitis in males is due to an underlying urethral abnormality • Congenital urethral valves in infants • Prostate enlargement in older men Cystitis Clinical presentation • Acute cystitis with ulceration Acute cystitis A
Cystitis:
Predisposing Factors
• Predisposing conditions include: ➢Pregnancy ➢Intercourse with urethral trauma ➢Poor toilet hygiene ➢Diabetes mellitus ➢Instrumentation and catheterization
Cystitis:
Clinical Picture
Dysuria • Frequency • Nocturia • Urgency • Sometimes supra-pubic pain and tenderness • Usually no fever
Acute Pyelonephritis:
Definition
Defined as infection of the renal pelvis and parenchyma • Important cause of renal disease • Also a commonly undiagnosed cause of death in diabetic patients
Acute Pyelonephritis:
Pathogenesis
Pathogenesis of acute pyelonephritis • Ascending infection: starts as an acute cystitis with damage to the vesicoureteral valves, causing reflux of infected urine that results in ureteritis and subsequent pyelitis (inflammation of the renal pelvis), followed by spread of infection through collecting tubules into renal parenchyma Pathogenesis of acute pyelonephritis Pathogenesis of acute pyelonephritis • Haematogenous spread from another infection through septicaemia or pyaemia • Examples include: ➢Infective endocarditis ➢Pneumonia ➢Osteomyelitis • Here the infection begins in the renal parenchyma and then spreads later to the renal pelvis • Both kidneys are usually involved
Acute Pyelonephritis:
Clinical Picture
Clinical presentation • Symptoms of cystitis may be present, i.e. dysuria, frequency, nocturia and urgency • Patients are usually febrile • Flank pain with renal angle tenderness
Acute Pyelonephritis:
Pathology-Macroscopy
Pathology of acute pyelonephritis • Macroscopic appearance: ➢Kidneys are enlarged, red and oedematous ➢Small yellow subcapsular abscesses may be present ➢Cut-section may show yellow lines of suppuration stretching up from papillae ➢Pelvic mucosa is hyperaemic and oedematous ➢Urine is turbid or frankly purulent Kidney surface with multiple subcapsular abscesses Abscess within renal parenchyma
Acute Pyelonephritis:
Pathology-Microscopy
Pathology of acute pyelonephritis • Microscopic appearance: - Neutrophils present within the renal tubules as well as the interstitium (infective tubulo-interstitial nephritis) - May show abscess formation - Glomeruli are normal
Acute Pyelonephritis:
Complications
Acute renal failure
• Recurrent episodes of acute infection with eventual
chronic pyelonephritis
• Papillary necrosis – decrease in medullary blood
flow especially common in diabetic patients or
where there is urinary tract obstruction
• Pyonephrosis whereby pus fills and distends the
entire renal pelvis, calyces and ureter (seen in total
urinary obstruction)
• Rupture of a subcapsular abscess with extension of
infection into the perinephric tissue
• Even septicaemia
Papillary Necrosis
Infection in the context of obstruction • Infection in the context of diabetes mellitus • Analgesic nephropathy (NSAID abuse - phenacetin) Prognosis of acute pyelonephritis •
Acute Pyelonephritis:
Prognosis
Prognosis is generally good with antibiotic treatment • Acute pyelonephritis may prove fatal if untreated • Some patients, particularly babies and elderly individuals, do not necessarily present with the classic symptoms of pyelonephritis, so remember to examine the urine with a dipstick
Chronic Pyelonephritis:
Introduction/Definition
Chronic pyelonephritis is fairly common
Usually seen in adults
One of the most common causes of chronic renal failure
Chronic Pyelonephritis:
Aetiology and Pathogenesis
• Usually develops as a complication of repeated attacks of acute pyelonephritis • Also occurs in chronic urinary tract obstruction that predisposes to ascending urinary infections: ➢Calculi (kidney stones) ➢Tumours ➢Prostate enlargement ➢Ureteral strictures • Congenital vesico-ureteric reflux
Chronic Pyelonephritis:
Vesico-ureter Reflux
Vesico-ureteric reflux is a congenital abnormality of the terminal portion of the ureter
Presents in early childhood
The high pressure in the renal pelvis causes intra-parenchymal reflux with parenchymal scarring
Chronic Pyelonephritis:
Pathology-Macroscopic
• Macroscopic appearance ➢Unilateral or bilateral involvement depending on the pathogenesis ➢Kidney is small ➢Kidney shows numerous large, irregular cortical scars ➢The renal pelvis and calyces are deformed and often dilated (hydronephrosis) with accompanying pressure atrophy of renal cortex
Chronic Pyelonephritis:
Pathology-Microscopic
Chronic inflammatory cell infiltrate in the
kidney interstitium, i.e. lymphocytes and
plasma cells
➢Interstitial fibrosis
➢Tubules are atrophic
➢Some tubules are dilated and filled with hyaline casts, which resembles the thyroid gland (called thyroidization)
➢Glomeruli show secondary changes, such as
glomerular sclerosis and peri-glomerular fibrosis
Chronic Pyelonephritis:
Complications
Chronic renal failure
Secondary hypertension
Bilharzia:
Incidence
All ages
In South Africa, bilharzia is very
common in the provinces north of the
Vaal River, as well as in the northern
regions of Kwa Zulu Natal
Bilharzia:
Pathogenesis
Bilharzia caused by the trematode (fluke) Schistosoma haematobium
Bilharzia seen where fresh water has become contaminated by Schistosoma
People bathing or swimming in such water are at risk
Lifecycle involves the fresh water snail and the human
Schistosoma ova (eggs) are excreted in the urine into the water
Ovum releases a motile ciliated miracidium that enters an aquatic snail host
After a period of development within the snail
host, the cercaria are released, and these penetrate the skin of people in the water
The cercaria, now called schistosomules,
migrate to the lungs where they mature into adult worms
Adult worms usually migrate to the portal vessels where they mate
The adult female fluke then migrates to the venous plexus around the bladder
The ova (eggs) are laid in the bladder wall
The eggs secrete enzymes that dissolve host
tissues in the vicinity, and so doing allows the
eggs to enter the bladder lumen, where they
can be excreted in the urine, and so perpetuate
the cycle
Live bilharzia eggs elicit an acute inflammatory
reaction
Once the eggs die and calcify, they elicit a
granulomatous response as well as fibrosis
Bilharzia:
Clinical Presentation
The most important clinical feature in bilharzial cystitis is haematuria
Bilharzia:
Pathology-Macroscopy
Mucosa of the bladder and ureters becomes thickened and granular, i.e. a ‘wet sand’ appearance macroscopically
Ureters may become stenotic because of
the fibrosis
Bilharzia:
Pathology-Microscopy
Bilharzia ova present in mucosa, viable or
calcified
Acute inflammation with eosinophils
Granulomas with foreign body-type giant cells
Later fibrosis
Overlying transitional epithelium undergoes
squamous metaplasia
Bilharzia:
Complications
• Squamous cell carcinoma of bladder
• Fibrosis of ureter(s) causes ureter
obstruction, which leads to hydronephrosis
and predisposes to ascending bacterial
infections of the urinary tract, such as
pyelonephritis
• In a heavy Schistosoma infestation, eggs
may enter the systemic venous circulation,
i.e. vesical venous plexus to inferior vena
cava, and so embolise to the lungs, causing
pulmonary hypertension
Renal Tuberculosis
Uncommon
Secondary to pulmonary tuberculosis
Two types:
1.Miliary tuberculosis
2.Isolated organ tuberculosis, called
tuberculous pyelonephritis, which may be
uni- or bilateral, and shows extensive
caseation and destruction of the kidney
Glomerular Disease/Glomerulopathy:
Definition/Introduction
The term glomerulopathy includes several diseases that affect the glomeruli (inflammatory and non-inflammatory)
Glomerulonephritis refers to inflammatory disease /
inflammation of the glomerulus.
These diseases have different aetiologies, different
morphologic appearances and varying prognoses
The glomerulopathies may also clinically present in
different ways
Some glomerulopathies resolve and have a good prognosis, but other cases follow a chronic course, resulting in a chronic glomerulonephritis /-opathy with eventual chronic renal failure (such patients require dialysis and/or renal transplantation)
