Urinary and Renal Disorders (Part 3)

Renal Function Tests

Renal Concentration

- Specific gravity

- Urine osmolality

Creatine clearance

- 24-h urine

Serum

- Creatinine level

- BUN

- BUN to creatinine ratio

specific gravity

a measure of the degree of concentration of the urine

1.005-1.025

normal value of urine specific gravity

urine osmolality

Concentrating ability is lost early in kidney disease; hence, these test findings may disclose early defects in renal function.

creatinine clearance

- detects and evaluates progression of kidney disease

- test measures volume of blood cleared of endogenous creatinine in 1 min, which provides an approximation of the GFR

- sensitive indicator of kidney disease used to follow progression of kidney disease

creatinine level

- measures effectiveness of renal function

- remains fairly constant in the body

creatinine

- the end product of muscle energy metabolism

- regulated and excreted by the kidneys

BUN

- serves as index of renal function

- affected by protein intake, tissue breakdown, and fluid volume changes

BUN to creatinine ratio

- evaluates hydration status

- elevated = hypovolemia

- normal ratio, elevated BUN and creatinine = intrinsic kidney disease

0.6-1.2 mg/dL

normal value of creatinine in males

0.4-1.0 mg/dL

normal value of creatinine in females

8-20 mg/dL

normal value of BUN

8-23 mg/dL

normal value of BUN in patients >60 years old

about 10:1

normal value of BUN to creatinine ratio

uric acid

- a chemical created when the body breaks down substances called purines

- most dissolves in blood and travels to the kidneys which passes out in urine

purines

- normally produced in the body and are also found in some foods and drinks

- food with high content: liver, anchovies, mackerel, dried beans and peas, and beer

hyperuricemia

high level of uric acid in the blood

3.5-7.2 mg/dL

normal value of uric acid

Renal Replacement Therapy

- becomes necessary when the kidneys can no longer remove wastes, maintain electrolytes, and regulate fluid balance

- need can be acute or chronic

- includes the various types of dialysis and kidney transplantation

dialysis

types:

- hemodialysis (HD)

- continuous renal replacement therapy (CRRT)

- peritoneal dialysis (PD)

acute dialysis/urgent dialysis

indications:

- a high and increasing level of serum potassium

- fluid overload

- impending pulmonary edema

- increasing acidosis

- pericarditis

- advanced uremia

acute dialysis/urgent dialysis

may also be used to:

- remove medications or toxins (poisoning or medication overdose) from the blood

- for edema

- hypertension that does not respond to other treatment

- hyperkalemia

hemodialysis

used for:

- patients who are acutely ill and require short term dialysis for days to weeks until kidney function resumes

- patients with advanced CKD and ESKD who require long-term or permanent renal replacement therapy

hemodialysis

prevents death but does not cure kidney disease and does not compensate for the loss of endocrine or metabolic activities of the kidneys

hemodialysis

- most patients receive this intermittently

- involves treatments three times a week with an average treatment duration of 3 to 4 hours in an outpatient setting

hemodialysis

- can also be performed at home by the patient and a caregiver

- if at home, treatment time and frequency can be adjusted to meet optimal patient needs

diffusion

- process in which toxins and wastes in the blood are removed by dialysis

- move from an area of higher concentration in the blood to an area of lower concentration in the dialysate

hemodialysis

objectives:

- to extract toxic nitrogenous substances from the blood

- to remove excess fluid

dialyzer

- artificial kidney

- a synthetic semipermeable membrane through which blood is filtered to remove uremic toxins and a desired amount of fluid

hemodialysis

principles:

- diffusion

- osmosis

- ultrafiltration

dialyzer

- hollow-fiber devices containing thousands of tiny capillary tubes that carry the blood through the artificial kidney

- porous and act as a semipermeable membrane, allowing toxins, fluid, and electrolytes to pass across the membrane

hemodialysis

the blood, laden with toxins and nitrogenous

wastes, is diverted from the patient to a machine via the use of a blood pump to the dialyzer, where toxins are filtered from the blood and the cleansed blood is returned to the patient

constant flow of the solution

maintains the concentration gradient to facilitate the exchange of wastes from the blood across the semipermeable membrane into the dialysate solution, where they are removed and discarded

vascular access devices

- provides immediate access to the patient's circulation for acute hemodialysis

- achieved by inserting a double-lumen, noncuffed, large-bore catheter into the subclavian, internal jugular, or femoral vein by the physician

- double-lumen, cuffed catheters may also be inserted into the internal jugular vein

arteriovenous fistula (AVF)

- preferred method of permanent vascular access for dialysis

- created surgically (usually in the forearm) by joining (anastomosing) an artery to a vein, either side to side or end to side.

arteriovenous fistula (AVF)

arterial segment = arterial flow to the dialyzer

venous segment = reinfusion of the dialyzed blood

arteriovenous grafts

- established by connecting the artery and vein using synthetic tubing

- can be created by subcutaneously interposing a biologic, semibiologic, or synthetic graft material between an artery and vein

arteriovenous grafts

- usually created when the patient's vessels are not suitable for creating of an AVF

- usually placed in the arm but may be placed in the thigh or chest wall

Peritoneal Dialysis

goals:

- to remove toxic substances and metabolic wastes

- to reestablish normal fluid and electrolyte balance

Peritoneal Dialysis

- may be the treatment of choice for patients with kidney disease who are unable or unwilling to undergo hemodialysis or kidney transplantation

- may successfully treat severe hypertension, heart failure, and pulmonary edema not responsive to usual treatment regimens

peritoneal membrane

- covers the abdominal organs and lines

- serves as the semipermeable membrane in PD

sterile dextrose dialysate fluid

introduced into the peritoneal cavity through an abdominal catheter at established intervals

clearance

movement of solute from the blood into the dialysate fluid

Ultrafiltration

- water removal

- occurs in PD through an osmotic gradient created by using a dialysate fluid with a higher glucose concentration than the blood

dwell time

when the dialysate is in the peritoneal cavity

Peritoneal Dialysis

Acute Complications

1. Peritonitis

2. Leakage

3. Bleeding

Peritoneal Dialysis

Long-Term Complications

1. Hypertriglyceridemia

2. Cardiovascular disease

3. abdominal hernias

and aggravates symptoms of hiatal hernia and hemorrhoids

4. Low back pain and anorexia

5. Mechanical problems

Peritoneal Dialysis

Approaches:

1. Acute intermittent peritoneal dialysis

2. Continuous ambulatory peritoneal dialysis (CAPD)

3. Continuous cyclic peritoneal dialysis (CCPD)

Urinary diversion

a surgical procedure that creates a new way for urine to exit your body when urine flow is blocked or when there is a need to bypass a diseased area in the urinary tract

cystectomy

bladder to be removed

Urinary diversion

indications:

- bladder cancer

- Nerve damage to the bladder

- Chronic—or long lasting—inflammation of the bladder

- conditions that cause outside pressure to the urethra or one or both ureters