Histo: Urology Flashcards
What are urinary calculi?
Crystal aggregates in the renal collecting ducts.
What is the epidemiology of urinary calculi?
- 15% lifetime incidence
- M:F = 3:1
List the three main types of urinary tract calculi in order of prevalence.
- Calcium oxalate (Weddelite) - 75%
- Magnesium ammonium phosphate (Struvite) - 15%
- Urate - 5%
What is the basic mechanism behind the formation of calcium oxalate stones?
Increased urinary calcium concentration (hypercalciuria)
List some underlying conditions that can lead to the formation of calcium oxalate stones.
- Absorptive hypercalciuria - excessive calcium absorption from the gut
- Renal hypercalciuria - impaired absorption of calcium in the proximal renal tubule
- Hypercalcaemia e.g. hyperparathyroidism (RARE)
Describe how magensium ammonium phosphate stones (triple stones) are formed.
- Results from infection by a urease-producing organism (e.g. Proteus)
- Ammonia produced by the bacteria alkalinises the urine leading to precipitation of magnesium ammonium phosphate stones
- They can become very large (e.g. staghorn calculi)
Which patients are predisposed to the formation of urate stones?
Conditions causing hyperuricaemia
- Gout
- Rapid cell turnover (e.g. chemotherapy)
Most patients do not actually have hyperuricaemia or increased uric acid excretion in urine
- Believed to be due to tendency to produce slightly acidic urine
What are 3 common presentations of urinary calculi?
- Haematuria
- Colic
- Recurrent UTI
Where do urinary calculi stones tend to get stuck within the urinary tract?
- Pelvic-ureteric junction
- Pelvic brim
- Vesico-ureteric junction
This causes renal colic symptoms
What are the consequences of large stones?
- Obstruction
- Risk of infection
- CKD
This is because large stones tend to get stuck in the kidney
List three types of benign renal neoplasm.
- Papillary adenoma
- Renal oncocytoma
- Angiomyolipoma
Define papillary adenoma.
Benign epithelial kidney tumour with a papillary or tubular architecture
- They must be <15 mm in size
- Well-circumscribed
- Linked to papillary renal cell carcinoma
Frequent found incidentally in nephretomies and autopsies (especially in those with damaged kidneys e.g. CKD)
What are the genetic associations of papillary adenomas?
- Trisomy 7 and 17
- Loss of Y chromosome (can occur in the cells of men with age)
What is a renal oncocytoma?
- Benign epithelial kidney tumour composed of oncocytic cells
- They are usually well-circumscribed and usually sporadic
NOTE: often an incidental finding
Oncocytes are cells that have accumlated numerous mitochondria
Name a syndrome that is associated with renal oncocytoma.
Birt-Hogg-Dubé syndrome
Describe the histological appearance of oncocytes.
- Large cells
- Pink (eosinophilic) granular cytoplasm (due to numerous mitchondria)
- Prominent nucleolus
What is an angiomyolipoma?
Benign mesenchymal kidney tumour composed of thick-walled blood vessels, smooth muscle and fat
- Derived from perivascular epitheloid cells
- Mostly sporadic
NOTE: often an incidental finding but may cause flank pain, haemorrhage and shock (if >4cm)
Which hereditary condition is associated with angiomyolipoma?
Tuberous sclerosis
What is renal cell carcinoma?
Malignant epithelial kidney tumour
List some risk factors for renal cell carcinoma.
- Smoking
- Hypertension
- Obesity
- CKD requiring long-term dialysis
- Genetic (e.g. von Hippel Lindau)
How does renal cell carcinoma tend to present?
- Painless haematuria (50% of cases)
- Remaining cases are detected incidentally on imaging
Name the subtypes of renal cell carcinoma in order of prevalence.
- Clear cell renal cell carcinoma (70%)
- Papillary renal cell carcinoma (15%)
- Chromophobe renal cell carcinoma (5%)
What are clear cell renal cell carcinoma.
- Epithelial kidney tumour composed of nests of clear cells set in a delicate capillary vascular netwrok
- Grossly apears golden-yellow with haemorrhagic areas
What is a common cytogenetic finding in clear cell renal carcinoma?
Loss of chromosome 3p
What are papillary renal cell carcinoma?
Epithelial kidney tumour composed of papillae and/or tubules
- By definition >15mm in size
- Cytogenetics show trisomy 7 and 17, and loss of Y chromosome
- 2 histological subtypes
- They appear grossly as a fragile, friable brown tumour
NOTE: this is the malignant counter part of papillary adenoma.
Describe the histological appearance of the two types of papillary renal cell carcinoma.
- Type 1: composed of a single layer of small and flat cells. You see a lot of islands of cells.
- Type 2: there is pseudostratification of the cells
NOTE: type 2 tends to have a worse prognosis than type 1