Acute renal failure should be coded separately with the appropriate code from category 584. Assign the code 403.X1 if the patient has chronic renal failure documented by the physician. In other words, the relationship between hypertension and heart disease must be stated, while the relationship between hypertension and renal disease is assumed. See fifth digits 0-3 in the tabular listing. See OCG 4.10.
Many coders incorrectly assume that hypertensive crisis is accelerated hypertension.
Secondary hypertension accounts for about 5 percent of all patients suffering from hypertension. Causes may be varied and include estrogen use, renal disease, renal vascular hypertension, primary hyperaldosteronism and Cushing's syndrome, pheochromocytoma, coarctation of the aorta, hypertension during pregnancy, as well as others. According to OCG 4.7, secondary hypertension requires the assignment of two codes, one identifying the etiology of the hypertension and one from category 405, Secondary hypertension. Sequencing is dependent upon the circumstances of the admission. Transient hypertension or elevated blood pressure should be assigned to code 796.2, Elevated blood pressure without diagnosis of hypertension.