The metabolic consequences of diabetes mellitus are directly responsible for many well recognized and chronic complications in several organ systems, such as retinopathy, neuropathy, and nephropathy. The precise documentation and code assignment of diabetes and its complications can have a profound impact on revenue and quality reporting for both clinicians and hospitals.
Last month's column provided an overview, definitions, coding, and documentation of diabetes, its six types, and its acute complications. This column will address chronic diabetic complications, focusing on type 2 diabetes, with the understanding that the same principles apply to the other types.
ICD-10-CM recognizes several categories of chronic complications (see Table).
Diabetic nephropathy (E11.2), or glomerulosclerosis due to glomerular injury, commonly affects diabetic patients, leading to chronic kidney disease (CKD). Diabetes is the top cause of CKD and end-stage renal disease worldwide. The characteristic finding is albuminuria, defined as an albumin excretion rate of at least 30 mg/24 h or an albumin-to-creatinine ratio of at least 30 mg/g. Papillary (medullary) necrosis is another manifestation of diabetic nephropathy, but acute tubular necrosis is not caused by diabetes. The type of nephropathy (nearly always CKD) is coded with the E11.2 code. The stage of CKD is incorporated in the CKD codes (N18.1-N18.6).
Diabetic retinopathy (E11.3) is one of the most important causes of visual loss worldwide and includes microangiopathy, macular edema, hemorrhage from neovascularization, and retinal detachment. It has scores of codes identifying type, location, and severity. It may be classified as proliferative and nonproliferative. Diabetic glaucoma (E11.39) is caused by increased intraocular pressure resulting specifically from proliferative retinopathy. Diabetic cataract (E11.36) is primarily associated with type 2 diabetes.
Diabetic neuropathy (E11.4) includes mononeuropathy (peripheral or cranial), polyneuropathy, autonomic neuropathy, “unspecified neuropathy,” and diabetic amyotrophy. Peripheral polyneuropathy and autonomic neuropathies are probably the most common complication of diabetes, and conversely, diabetes is the most common cause of these neuropathies.
Diabetic circulatory disease (E11.5) includes peripheral vascular disease (PVD) and microangiopathy. PVD is a progressive atherosclerosis of lower-extremity arteries (generally not upper extremities), eventually progressing to distal tissue ischemia. Carotid, aortic, renal, mesenteric, and coronary arteries are central arteries, not peripheral. Microangiopathy represents toxic injury to vascular and capillary endothelium due to hyperglycemia.
Arthropathy (E11.6), primarily Charcot joint, is chronic, progressive joint destruction due to absent sensation leading to repetitive unrecognized joint injury and degeneration. It primarily affects the foot and ankle but is also seen in the shoulder. Other diabetic arthropathic conditions include carpal tunnel syndrome, trigger finger (stenosing tenosynovitis), Dupuytren's contracture, adhesive capsulitis (frozen shoulder), and calcific periarthritis/tendinitis.
Diabetic skin ulcers (E11.62) are nonpressure, nonischemic ulcers of the foot, usually related to sensory neuropathy. The foot is the most common location, although they also occur on the buttocks, back, and other parts of the lower extremities. The connection between foot ulcers (E11.621) and diabetes is assumed by ICD-10-CM. Ulcers in other locations (E11.622) should be specified as diabetic or due to diabetes for proper assignment to the E11.62 categories. Almost all foot and lower-extremity ulcers among diabetic patients are due to their diabetes, except those on the heel (almost always a pressure ulcer) or over bony deformities. Other less common skin complications coded under E11.62 include necrobiosis lipoidica, diabetic dermopathy, granuloma annulare, and eruptive xanthomatosis.
Oral complications (E11.63) of diabetes, predominately periodontal disease, include periodontitis and gingivitis, occasionally leading to osteomyelitis. Dry mouth (sicca syndrome) is another oral complication due to salivary gland destruction, causing a predisposition to cavities (dental caries), periodontal disease, and oral candidiasis. These can be specified as diabetic oral complications. Prudent clinicians will regularly look for and document diabetic oral complications and make sure treatment is discussed or provided.
Other specified complications (E11.89) are those not specifically covered by other diabetes complication codes, including osteomyelitis, diabetic hyperlipidemia, and other conditions specified by clinicians as diabetic complications. Code E11.89 is assigned, plus a code for the specified complication. The code for “unspecified” complications (E11.8) is hardly ever used because any complication should always be specified in the record.
Osteomyelitis is presumed to be diabetic in origin, unless another cause is specified. Code E11.89 for other specified complications is assigned, plus a code for osteomyelitis that incorporates location (category M86).
Diabetic hyperlipidemia is fasting hypertriglyceridemia (>200 mg/dL and often >500 mg/dL) with HDL cholesterol levels below 40 mg/dL, specifically caused by diabetes. LDL cholesterol is not particularly elevated. The vast majority of diabetic patients with hyperlipidemia do not have diabetic hyperlipidemia, but rather the common forms of elevated cholesterol unrelated to diabetes. Diabetic hyperlipidemia does not have its own ICD-10-CM code because it is assigned as an “other specified” complication (E11.89), plus the code for “hyperlipidemia” to make clear what the specified complication is. Clinicians should specifically document “diabetic hyperlipidemia” or “hyperlipidemia due to diabetes” somewhere in the note to link these two diagnoses.
In summary, the proper documentation and coding of diabetes and its complications have a significant impact on quality reporting and sometimes on reimbursement. A clear understanding of authoritative diagnostic standards and the impact of diagnostic terminology on code assignment are essential for accuracy.