Flashcards in WEEK 3 Deck (64)
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KIDNEY BACKGROUND
- Maintain stable internal environment for cell/ tissue metabolism→ filter blood and eliminate waste
- Produce urine; contributes to homeostasis of blood volume
- Waste products→ metabolites formed during chemical reactions, toxins, excess electrolytes
- Endocrine function→ secrete hormones→
Renin (blood pressure)
- Erythropoietin (erythrocyte production)
1.25-dihydroxyvitamin D3 (calcium metabolism)
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KIDNEY ANATOMY
- 3 distinct sections→ cortex, medulla and pelvis
- Outer layer of kidney→ cortex
- Medulla→ inner part of kidney and consists of regions called pyramids (cone shaped structures)
- Minor and major calyces are chambers that receive urine and form the entry into the renal pelvis
- The pelvis connects to the ureters for urine to flow into the bladder for storage
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NEPHRON
- Functional unit of the kidney (Each kidney has over 1 million nephrons)
- Units are responsible for producing urine → glomerular filtration and tubular reabsorption and secretion
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3 PROCESSES IN THE FORMATION OF URINE
- Glomerular filtration: Filtration of plasma at the glomerulus
- Tubular reabsorption: Reabsorption of various substances along tubular structures
- Tubular secretion: Secretion of solutes into the tubules
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3 PROCESSES IN THE FORMATION OF URINE: Glomerular filtration: Filtration of plasma at the glomerulus
- Passive process; fluid and solutes (filtrate) move across membrane by hydrostatic pressure
- Filtrate contains electrolytes (sodium, chloride, potassium) and organic molecules (creatinine, urea, glucose)
- 2 forces oppose filtration effects of glomerular capillary hydrostatic pressure
Hydrostatic pressure in the glomerular space
- Osmotic pressure of the glomerular capillary blood
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3 PROCESSES IN THE FORMATION OF URINE: Tubular reabsorption: Reabsorption of various substances along tubular structures
- Filtrate flows into proximal convoluted tubule ready for reabsorption
- Due to processes such as simple diffusion, facilitated diffusion, active transport, co-transport and osmosis
- A large amount is reabsorbed back into the blood
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3 PROCESSES IN THE FORMATION OF URINE: Tubular secretion: Secretion of solutes into the tubules
- Molecules move into the tubules FROM the peritubular capillaries
- These are usually metabolism by-products that the body needs to remove
- Allows for other substances to be secreted AFTER glomerular filtration occurs
- Unlike glomerular filtration, this secretion process is selective
- Kidneys are an important organ in eliminating drugs from the body; these drugs are secreted in the tubules to be added to the urinary filtrate
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TYPES OF CAUSES OF ACUTE RENAL FAILURE (3)
- Prerenal
- Intrarenal
- Postrenal
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TYPES OF CAUSES OF ACUTE RENAL FAILURE: Prerenal description
- Problems upstream of kidneys→ alterations in renal blood flow
- Decreased blood flow to kidneys from
Trauma/ Major surgery
- Water loss from blood; dehydration or burns
- Heart Disease/ Decreased cardiac output
- Occlusion of small blood vessels in kidney
- Tubular necrosis can occur→ tubule cells sensitive to hypoxia
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TYPES OF CAUSES OF ACUTE RENAL FAILURE: Prerenal clinical manifestations
- Hypotension→ increase blood loss post surgery, severe burns or infection (sepsis) causing vasodilation
- Tachycardia
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TYPES OF CAUSES OF ACUTE RENAL FAILURE: Prerenal management
- Correction of fluid volume deficit
- Improvement of pump failure using inotropic agents
- If ischemia is fixed, patient supported on dialysis→ kidney function returns over next weeks
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TYPES OF CAUSES OF ACUTE RENAL FAILURE: Intrarenal description
- Associated with damage to kidney tissues
May occur as result of diseases affecting nephrons
- Glomerular disease, Medullary disease or Immune hypersensitivity disorders
- Toxic chemicals
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TYPES OF CAUSES OF ACUTE RENAL FAILURE: Intrarenal Clinical Manifestations
Hypertension
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TYPES OF CAUSES OF ACUTE RENAL FAILURE: Intrarenal Management
- Identification and removal of nephrotoxic agent
- Potentially dieuretics
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TYPES OF CAUSES OF ACUTE RENAL FAILURE: Postrenal Description
- Problems downstream of kidneys; obstructions to urine flow
- Caused by urine flow obstruction from both kidneys, at level of ureters urinary bladder or urethra
Hypertension (upstream)
- Damages blood vessels
- Causes decreased glomerular blood flow
- Stimulates the secretion of renin
- Causes further upstream effects → increased BP
- Ischaemic damage occurs within the kidney
- Kidney stones
- Enlargement of the prostate gland impedes the flow of urine in the urethra (downstream)
- Results in back pressure up the urinary tract
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TYPES OF CAUSES OF ACUTE RENAL FAILURE: Postrenal Clinical manifestations
- Hypertension by decreasing GFR
- Hydronephrosis→ When a kidney swells due to urine failing to properly drain from the kidney to the bladder as a result of a blockage /obstruction in urinary tract
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TYPES OF CAUSES OF ACUTE RENAL FAILURE: Postrenal Management
Identification and removal of cause of obstruction
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TYPES OF CAUSES OF ACUTE RENAL FAILURE: IRRESPECTIVE OF THE CAUSE→ CLINICAL MANIFESTATIONS
- Uraemia→ increased urea
- Pruritus→ Itching due to waste build up
- Oliguria or anuria→ little or no urine production
- Azotaemia→ High levels of nitrogenous compounds (e.g. urea, creatinine)
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CHRONIC RENAL FAILURE: DESCRIPTION
- It is the long term progressive and permanent loss of nephrons evident at >80% lost
- Nephron function is unrecoverable
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CHRONIC RENAL FAILURE: CAUSES
- Chronic glomerular disease
- Chronic medullary disease
- Diabetes mellitus
- Chronic hypertension
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CHRONIC RENAL FAILURE: MANAGEMENT
Management is dependent on reducing or stopping the disease progression
Cardiovascular issues
- Antihypertensives
- Erythropoietin injections
Electrolyte issues
- Low potassium diet for management of hyperkalemia with
- Phosphate binders for hypocalcemia and hyperphosphatemia
Renal issues
- A low protein diet for proteinuria
Metabolic Issues
- Dialysis for uraemia and acidosis
- Sodium bicarbonate for acidosis
Other Issues
- EMLA cream and ultraviolet- B therapy for pruritus
- Management of calcium and phosphate levels for restless legs
- Dialysis→ haemodialysis and peritoneal dialysis
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BACTERIAL UTIs: DESCRIPTION
- Kidneys, ureters, bladder, urethra usually sterile→ maintained by frequent flushing action of urine
- Some resident bacteria exist in the distal urethra (near opening)
- UTI’s usually caused by bacteria and most arise from patients own bowel flora
- Pathogenic microbe enters urinary tract→ damages urethra lining→ ascends tract→ enters urinary bladder→ damage to bladder lining→ inflammation (cystitis)
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BACTERIAL UTIs: MECHANISMS OF SPREAD
- Haematogenous→ less often, the pathogen may be carried by the bloodstream from a distant focus of infection to the kidney in the bloodstream
- Ascending→ Most UTIs arise from patients own bowel flora. Bacteria from faeces can enter urinary tract at urethral opening, and ascend to bladder→ sometimes progresses higher up to kidneys
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BACTERIAL UTIs: DIAGNOSIS
- Investigations of urine (colour, smell and transparency)
- Test with a urinary dipstick to determine positive results for blood and nitrate (a characteristic product of bacterial metabolism)
- A midstream urine (MSU) sample
- A culture of the urine sample to identify the pathogen and determine its antibiotic sensitivity
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BACTERIAL UTIs: MANAGEMENT
- Removal or replacement of the catheter (often resolution of a UTI)
- Initial antimicrobial therapy with a broad-spectrum agent
- Encouraging fluid intake in order to help flush bacteria
- Urinary alkalisers may assist in reducing dysuria
- Cranberry as a supplement to reduce the adhesion of bacteria to the epithelial lining of the urinary tract
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KIDNEY MEDULLARY DISORDER: PYELONEPHRITIS: DESCRIPTION
- An infection and inflammation of the kidney
- Progression to chronic renal failure is inevitable
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KIDNEY MEDULLARY DISORDER: PYELONEPHRITIS: ACUTE
- An acute inflammation in the renal tubules and the interstitium due to a infectious cause
- The infection settles in the renal parenchyma→ Acute inflammation with neutrophils & oedema in the interstitium
- Phagocytes and inflammatory exudate move from the blood into the affected area, impeding tubule function.
- The papillae of the medullary pyramids may become necrotic
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KIDNEY MEDULLARY DISORDER: PYELONEPHRITIS: CHRONIC
Repeated infection causes gradual damage and loss of functional kidney tissue which is replaced by scar tissue
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KIDNEY MEDULLARY DISORDER: PYELONEPHRITIS: CLINICAL MANIFESTATIONS
- Dysuria- painful to urinate,
- Frequency and urgency of urination
- Flank pain
- High fever
- Tachycardia
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