100 Cases in Clinical Pathology Flashcards
Whar are the main differentials for sudden-onset polydypsia?
- Diabetes mellitus
- Diabetes insipidus
- Hypercalcaemia
- Primary polydypsia
What are the causes of non-visible haematuria?
Glomerular:
- Glomerulonephritis
- Other hereditary causes
Upper urinary tract:
- Nephrolithiasis
- Pyelonephritis
- Renal cell carcinoma
- Polycystic kidney disease
- Renal trauma
- Metabolic derangements such as hypercalciuria
Lower urinary tract:
- Bladder and prostate cancer
- Benign lesions such as BPH
- Bladder papillomas
- Urethritis
- Cystitis
What are the investigations for non-visible haematuria in secondary care?
Standard for all patients:
- Urine dip
- Urine MC&S
Upper urinary tract-specific:
- Ultrasound/CT systography
Lower urinary tract-specifc:
- Cystoscopy
What are the causes of hypertonic hyponatraemia?
Presence of osmotic agents in the blood drawing water out of cells. This occurs with hyperglycaemia and infusion of osmotic agents like mannitol.
What are the causes of isotonic hyponatraemia?
- Retention of isosmotic fluid in the extracellular space (e.g. isotonic glucose infusion)
- Severe hyperlipidaemia or hyperproteinaemia reduces the fractional water content, leading to a ‘pseudohyponatraemia’
What are the causes of hypotonic hyponatraemia?
Hypovolaemic:
- Sodium depletion by renal or extrarenal means
Normovolaemic:
- Sodium content is diluted by excess amounts of water
- SIADH
- Hypothyroidism
- Reduced solutes intake
Hypervolaemic:
- Retention of sodium and water due to activation of the renin-angiotensin-aldosterone system
- Congestive heart failure
- Liver cirrhosis
- Nephrotic syndrome
*
What are the criteria for diagnosing SIADH?
- Reduced plasma osmolality <275 mOsm
- Urine osmolality >100 mOsm
- Clinical euvolaemia
- Continued natriuresis >40 mM in the presence of…
- Normal thyroid and adrenal function, and
- Without recent use of diuretics
What are the causes of nephrotic syndrome?
Primary glomerular disease:
- Minimal change disease
- Membranous glomerulopathy
- Focal segmental glomerulosclerosis (FSGS)
- Membranoproliferative glomerulonephritis (MPGN)
Systemic diseases:
- Diabetes mellitus
- Amyloidosis
- Systemic lupus erythematosus
- Drugs (e.g. nonsteroidal anti-inflammatories [NSAIDs])
What conditions are associated with +ve ANA?
- Systemic lupus erythematosus (SLE)
- Scleroderma
- Rheumatoid arthritis
- Mixed connective tissue disease
- Sjögren’s syndrome
- Inflammatory myopathies, such as dermatomyositis and polymyositis
- Primary biliary cirrhosis
What are the criteria for a good screening test?
- The disease being screened should be an important health problem
- The natural history of the disease should be well understood
- There should be an identifiable early stage of disease
- Treatment at an early stage should be of more benefit than at a later stage
- There should be a suitable test to identify the early stage
- The test should be acceptable to the population
- The intervals for repeating the test should be well defined
- Suitable facilities should exist to account for the workload resulting from screening
- Risks of the test, both physical and psychological, should be less than the anticipated benefits
- Costs should be balanced against benefits
What are the causes of hypoglycaemia?
Non-fasting (occurs after meal):
- Gastrectomy/bypass surgery (which causes rapid gastric emptying with overproduction of insulin)
- Pancreatic islet cell hyperplasia
- Occult diabetes (deficient early insulin response in diabetes followed by exaggerated delayed response)
Fasting (between meals):
Hyperinsulinaemic state
- Insulin reaction or sulphonylurea overdose (the commonest cause)
- Autoimmune hypoglycaemia
- Surreptitious use of insulin or sulphonylureas
- Pancreatic β-cell tumours (typically insulinoma)
Non-hyperinsulinaemic state:
- Reduced hepatic gluconeogenesis, which may arise from liver disease or inborn
errors of metabolism - Renal insufficiency (the kidney contributes to gluconeogenesis too)
- Alcohol excess, which increases the activity of alcohol dehydrogenase (consuming
NAD+) and thereby limits the conversion of lactate to pyruvate, which is a
gluconeogenic substrate - Non-pancreatic tumours (e.g. retroperitoneal fibrosarcoma) that release IGF-2,
which can activate the insulin receptor
What is the metabolism of bilirubin?
What levels of serum bilirubin are required to produce jaundice?
>50 uM
What are the mechanisms of hyperbilirubinaemia?
- Excess production
- Reduced hepatic uptake
- Impaired conjugation
- Reduced hepatocellular excretion
- Impaired bile flow
What are the types of jaundice?
- Pre-hepatic. This causes an unconjugated hyperbilirubinaemia and arises from increased production of bilirubin (e.g. haemolysis, ineffective erythropoiesis).
- Hepatic. The hyperbilirubinaemia may either be conjugated or unconjugated depending on which part of the hepatic metabolic pathway is affected. Congenital causes include Gilbert, Crigler–Najjar, and Dubin–Johnson syndromes, while acquired causes include viral hepatitis, autoimmune hepatitis, alcoholic liver disease, drugs (e.g. halothane, paracetamol and methyldopa) and primary biliary cirrhosis.
- Post-hepatic. This typically causes a conjugated hyperbilirubinaemia and arises as a result of biliary obstruction, causes of which include gallstones, malignancy (pancreatic cancer, cholangiocarcinoma and ampullary tumours of the duodenum), biliary strictures, pancreatic pseudocysts, and sclerosing cholangitis.
What are the causes of hypercalcaemia?
- Hyperparathyroidism, which may be primary (e.g. parathyroid adenoma), secondary
(from renal failure leading to hyperphosphataemia and stimulation of parathyroid hormone [PTH] secretion), or tertiary (autonomous parathyroid activity
arising from secondary hyperparathyroidism) - Malignancy-associated, which may be either humorally mediated (e.g. release of PTHrP from squamous cell carcinomas) or osteolytic (e.g. multiple myeloma and bone metastases)
- Vitamin D-related (granulomatous diseases such as sarcoidosis, vitamin D excess)
- Drug-induced (e.g. thiazide diuretics)
- Endocrine disorders, including thyrotoxicosis
- Genetic disorders (e.g. familial hypocalciuric hypercalcaemia, FHH)
What are the most common causes of hypercalcaemia?
- Hyperparathyroidism
- Malignancy
- Together, these account for 90% of cases
How should hypercalcaemia be investigated?
- Investigate serum PTH
- If high, suspect primary or tertiary hyperparathyroidism
- If low, probably due to feedback suppression, suspect malignancy
- If inconclusive, look at serum vitamin D and serum ACE (sarcoidosis)
What is hirsutism?
Excessive terminal hair growth in a male pattern in women
What is a Ferriman–Gallwey scale?
- Scoring system used to determine amout of hair growth in androgen-dependent areas of the body
- A score of >7 is considered hirsutism
What are the causes of hirsutism in women?
Non-pathological:
- Idiopathic hirsutism (around 50% of cases)
Pathological:
- Polycystic ovarian syndrome
- Adrenogenital syndromes (e.g. nonclassic congenital adrenal hyperplasia)
- Androgen-secreting tumours,
- Causes of hormone over-production such as Cushing’s syndrome
- Drug-induced
What are important secondary causes of immunosuppression?
- Infections (e.g. HIV)
- Malnutrition
- Malignancy (especiially haematological)
- Drugs (e.g. immunosuppressants)
- Protein loss (e.g. nephrotic syndrome, protein-losing enteropathies)
- Metabolic diseases (e.g. diabetes, severe liver disease)
What are the common causes of primary immunodeficiency?
- Common variable immunodeficiency
- X-linked agammaglobulinaemia
- Selective Ig subclass deficiency
- Hyper-IgM syndrome
What is the normal range for anion gap?
10 - 18 mM
What are the common causes of metabolic acidosis with normal anion gap?
Metabolic acidosis with normal anion gap is caused by excess retention of H+ or loss of HCO3. Causes include:
- Increased losses of HCO3 from the gut (e.g. diarrhoea, via stomas)
- Increased losses of HCO3 from the kidney (e.g. carbonic anhydrase inhibitor therapy, proximal or type 2 renal tubular acidosis, tubular damage from drugs or paraproteins)
- Reduced renal excretion of H+ (e.g. distal or type 1 renal tubular acidosis, and type 4 renal tubular acidosis)
- Increased production of HCl (e.g. ingestion of ammonium chloride)
What are the pre-renal causes of AKI?
Arises from hypovolaemia leading to inadequate renal blood flow:
- Haemorrhage
- Sepsis
- Heart failure
- Diarrhoea
- Use of diuretics
What are the renal causes of AKI?
Intrinsic renal disease, which may affect the glomeruli:
- Glomerulonephritides
Intrinsic renal disease, which may affect the tubules and interstitium:
- Drugs such as NSAIDs and aminoglycosides
- Contrast media
- Intra-renal obstruction arising from renal calculi or the
cast nephropathy in multiple myeloma
What are the post-renal causes of AKI?
Post-renal obstruction, which leads to renal failure when both outflow tracts are obstructed or when one is obstructed in patients with a single kidney:
- Bladder outflow obstruction
- Ureteric calculi
- Intratubular crystal nephropathy
- Urothelial neoplasms