Q: Which one disease process need to be ruled out in severe pruritus associated with kidney failure, also known as Uremic pruritus?

Answer:  Hyperparathyroidism

If despite symptomatic treatment and increasing the dose/frequency of dialysis - uremic pruritus is not resolving, other disease processes particularly hyperparathyroidism need to be ruled out. Data is almost 45 years old but still is clinically relevant. 

References:

1. Massry S, Popovzer MM, Coburn JM, Mokoff DL, Maxwell MH, Kleeman CR. Interactable pruritus as a manifestation of secondary hyperparathyroidism in uremia. N Engl J Med1968; 279: 697–700

2. Hampers CL, Katz AI, Wilson RE, Merrill JP. Disappearence of uremic itching after subtotal parathyreoidectomy. N Engl J Med1968; 279: 695–697

3. Stahle‐Bäckdahl M, Hägermark O, Lins LE, Törring O, Hilliges M, Johansson O. Experimental and immunohistochemical studies on the possible role of parathyroid hormone in uremic pruritus. J Intern Med1989; 225: 411–415