Uremia and Azotemia
When kidney function (renal perfusion, filtration, and elimination of the bodyâ€™s metabolic wastes) deteriorates due to diabetes, hypovolemia, urinary tract obstruction, or other causes, the normally filtered waste products, urea, amino acids, creatinine, and other nitrates remain unfiltered and in the blood.
Elevated urea levels that arenâ€™t high enough to cause symptoms are called azotemia.Â Uremia is an elevation of urea in the blood that is high enough to cause symptoms, i.e., the â€śuremic syndrome.â€ť
Signs and symptoms of uremia are fatigue, nausea, muscle wasting, tremors, cognitive changes, and these are used to make the decision for the proper time to initiate dialysis. Chronic kidney disease (CKD) is a gradual process that ultimately ends in end-stage renal disease (ESRD). The symptom continuum that begins when azotemia progresses to uremia is unique to each patient, and the decision to initiate dialysis is also an individualized decision based on physician recommendation and patient preference.
Unless there are uremic heart or lung complications or cognitive changes which make dialysis mandatory, it is otherwise a difficult decision because it means a life-long therapeutic process that is time-consuming to the point of severely affecting oneâ€™s day-to-day activities of daily living and quality of life.
Process of Dialysis
There are two types of dialysis:
- Hemodialysis: a direct access to blood via a surgically implanted shunt or created arteriovenous fistula. It is typically done at a dialysis center where blood is pumped from the body, filtered by a machine, and then replaced. It is usually three times a week, each session taking 3-5 hours.
- Peritoneal dialysis: Uses an abdominal catheter and can be done by the patient at home and while traveling. A fluid that is instilled, when drained back out, will have metabolic wastes and excess salt and water drain with it. The collection of fluid in the abdomen, giving the symptom of bloating, is called a â€śdwell,â€ť and the recycling of new fluid for used fluid is called an â€śexchange.â€ť Peritoneal dialysis can be done all the time, as â€ścontinuous ambulatory peritoneal dialysis (CAPD) with manual discarding and refilling during the day and leaving the â€śdwellâ€ť overnight; or just overnight in a continuous cycling peritoneal dialysis (CCPD) done by a machine.
Diagnosis of Kidney Failure
Testing for kidney disease or kidney failure (end-stage renal disease, â€śESRDâ€ť) is done when signs and symptoms of kidney dysfunction prompt a history and physical exam to pursue an appropriate diagnosis. A careful medication history is important.
Edema (fluid retention), bloating, fatigue, tremors, and cognitive changes all require pursuit of a kidney disease diagnosis or its elimination among other possibilities. Also, ongoing heart failure and cirrhosis, which can injure the kidney, should prompt diagnostics. In renal vascular disease from atherosclerosis and hypertension, the renal component is part of the big picture in the diagnostic and therapeutic approach of cardiovascular components.
Tests for Kidney Function of Failure
- Urinalysis: A microscopic analysis of the urine to reveal casts (tubular-shaped debris from tubular disease in the kidney), red blood cells, white blood cells, and misshapen red blood cells; also, biochemical testing for albumin/protein.
- Blood metabolic profile to identify abnormalities of electrolytes, BUN (blood urea nitrogen), and serum creatinine (for a BUN/creatinine ratio).
- Albumim-to-creatinine ratio.
- Ultrasound to identify obstruction or chronic changes of kidney disease. An obstruction will take management into a mechanical direction of relieving the obstruction; alternately, without obstruction, a negative ultrasound prompts a flowsheet of decisions based on whether or not there is pus (nephritis) in the urine (pyuria).
- Kidney biopsy in cases of acute changes on imaging.
The glomerular filtration rate (GFR) is a quantitation of kidney function, determined by the sum of all of the functioning nephrons (filtering kidney cells). It is a number of mL filtered per minute multiplied by a constant of body size. Actual measurement is cumbersome and complicated, so most frequently GFR is done via quick estimations using formulas of creatinine clearance and serum creatinine.
Once the GFR becomes low enough, symptoms of uremia can emerge which will prompt a decision to begin dialysis.
What Is Dialysis Management?
Dialysis involves invasive retrieval of blood, filtering it outside of the body, and returning it (in hemodialysis), or it involves invasive irrigation of the abdomen to dilute toxins that decrease with repeated exchanges until cleared (in peritoneal dialysis).
Both peritoneal dialysis and hemodialysis can replace each other when there is a failure:
- Hemodialysis complication of thrombus, infection, or obstruction.
- Peritoneal complication of catheter malfunction requiring replacement or peritonitis from an introduced infectious agent during one of the many procedures.
For end-stage renal disease (ESRD), kidney transplant is the treatment of choice, but the candidates require careful evaluation since most of these patient have severe co-morbidities, such as diabetes, heart disease, etc., which will impact peri-surgical risk, post-transplant patient morbidity and survival, or survival of the transplanted kidney. Kidney transplant success relies on timely resumption of function of the implanted kidney and absence of antibodies that affect rejection.Â Patients are immunosuppressed to increase the chances of organ survival.
Prevention of Dialysis
Peritoneal dialysis is via an inserted tube, and sterile technique is necessary to prevent the introduction of infectious bacteria that could cause peritonitis. Infection is the most important and most frequent complication from peritoneal dialysis.
The catheter is the operational component to this type of dialysis, and catheter removal may be necessary when there is outflow failure, a leak, catheter cuff extrusion, abdominal wall hernia at the insertion site, or intestinal perforation. Hemodialysis may be necessary while awaiting replacement of a catheter or until any infection is cleared. Emergency surgery may be necessary to prevent loss of bowel or drain intra-abdominal abscesses.
Hemodialysis requires a surgically created access point for blood retrieval and return, either an implanted shunt or the establishment of an arteriovenous fistula.
Management and treatment of kidney disease using hemodialysis requires inspection and maintenance of the shunt, prevention of clots or infection, and assurance of patency. Anticoagulant therapy may be necessary if there is thrombus formation in the shunt or fistula. Removal of a shunt is indicated if it is colonized by bacteria.
Prevention of peritoneal dialysis-related complications, for the most part, requires strict sterile technique and periodic assessment of the catheter.
Prevention of kidney transplant failure requires immunosuppression and aggressive management of comorbidities that could threaten the implanted kidney, such as diabetes, dyslipidemia, and diabetes.