Renal Flashcards
(21 cards)
What maintains continence?
Urethral sphincters.
Describe the internal urethral sphincter.
It is mainly smooth muscle controlled by the autonomic nervous system (sympathetic-contraction, parasympathetic-relaxation).
Describe the external urethral sphincter (EUS).
It is mostly pelvic floor skeletal muscle under voluntary control. It holds the urine in check. Incompetence of the urethral sphincter (mainly EUS) is a major factor causing incontinence.
What is stress incontinence?
Due to loss of pelvic floor support and incompetence of the urethral sphincter; decreased urethral spincter tone, urethral hypermobility. symptoms include leaking with coughing, lifting, and sneezing.
Risk factors for incontinence.
Postmenopausal women have estrogen deficiency, which can causes laxity & weakness of pelvic floor support. Other risk factors for incontinence in women include obesity, co-morbidities (e.g., diabetes, stroke) & genitourinary surgery (e.g., hysterectomy).
Describe overflow incontinence.
Incomplete emptying and persistent involuntary dribbling. It is due to impaired detrusor contractility (e.g, diabetic autonomic neuropathy) or bladder outlet obstruction (e.g., tumor obstructing urethra) causing incomplete bladder evacuation. Post void residual urine volume is usually high.
Describe urge incontinence.
Sudden, overwhelming urge to urinate. It is due to detrusor overactivity. Triggers can include running water, hand washing, or exposure to cold weather. Loss of inhibitory CNS input to the bladder, due to frontal lobe & internal capsule infarcts, commonly cause detrusor hyperreflexia & urge incontinence.
What symptoms are diagnostic of stress incontinence?
Increased abdominal pressure (e.g., coughing, sneezing, or vigorous effort) greater than the urethral sphincter pressure can cause brief involuntary urine loss.
An essential pathologic step in crescent formation.
Fibrin deposition within Bowman’s space. Finding of crescents on light microscopy is diagnostic of rapidly progressive glomerulonephritis (RPGN).
What do the crescents in RPGN consist of?
Proliferated glomerular parietal cells, monocytes, and macrophages that have migrated into Bowman’s space, as well as abundant fibrin between the cellular layers of the crescents. As the disease progresses, crescents become sclerotic and obliterate Bowman’s space, thus impeding glomerular function. Renal injury is irreversible.
What are characteristic findings in type 1 RPGN (Goodpasture syndrome)?
C3 and IgG are deposited along the glomerular basement membrane. C4 deposition is usually not found.
What are the dibasic amino acids?
Cysteine, ornithine, lysine, and arginine (COLA). They share a common transporter in the intestinal lumen and kidneys. In patients with cystinuria, this transporter is defective, resulting in impaired renal and intestinal absorption of these amino acids.
Why don’t patients develop amino acid deficiencies?
COLA amino acids are absorbed in sufficient quantities as oligopeptides in the intestine.
Describe cystine kidney stone formation.
In the kidneys, impaired tubular reabsorption of COLA amino acids leads to a high urinary cystine concentration, resulting in the formation of cystine kidney stones. The other amino acids (OLA) are relatively soluble in urine and do not result in the formation of kidney stones.
What does parasympathetic stimulation do in the micturition reflex?
It causes detrusor muscle contraction and internal urethral sphincter relaxation.
What does sympathetic stimulation do in the micturition reflex?
It causes internal sphincter contraction and also helps with sensing a full bladder.
What regions in the brain inhibit the micturition reflex?
MS is likely an AI disease that causes varying degrees of demyelination, inflammation, and gliosis in the central nervous system (e.g., optic nerves, spinal cord, brainstem, periventricular white matter, and cerebellum). Regions in the pons and cerebral cortex partially inhibit the micturition reflex and also regulate contraction/relaxation of the external urethral sphincter. Patients typically develop a frequent urge to urinate and pass a small amount of urine. As MS progresses, the bladder can become atonic and dilated leading to overflow incontinence.
What can cause osmotic diuresis?
It can be due to hyperglycemia in uncontrolled diabetes mellitus and cause polyuria.
What is the blood sugar threshold for osmotic diuresis?
Blood sugar greater than 250mg/dL.
What are the epidemiological stats for stress incontinence?
The most common form of incontinence and typically presents after age 45. Almost twice as common in women b/c external urethral sphincter trauma or pudendal nerve (innervates EUS) injury is common during vaginal child birth.
What is the association between MS and urge incontinence?
Patients with MS most commonly develop urge incontinence due to loss of CNS inhibition of detrusor contraction in the bladder. As the disease progresses, the bladder can become atonic and dilated, leading to overflow incontinence.
