Excess nitrogenous waste products in the blood and their toxic effects. Kidney impairment (seeBright disease; diabetes mellitus; hypertension; kidney failure; nephritis) or disorders that hinder urine excretion (e.g., prostatic disorders) allow urea and other protein waste products to accumulate. Symptoms usually start with fatigue and loss of concentration. They may include itching and muscle twitches; dry, flaky, yellowish skin; dry mouth, metallic taste, and ammonia breath; and nausea, vomiting, diarrhea, and constipation. Advanced stages affect the nervous, cardiovascular, and respiratory systems and can lead to hypertension, seizures, heart failure, and death. If the underlying disorder cannot be treated, dialysis or kidney transplant may be required.