C h a p t e r 3 3
Diabetes Mellitus and the Metabolic Syndrome
815
occasionally severe “burning pain,” particularly at night,
can become physically and emotionally disabling.
53
Autonomic Neuropathy.
The autonomic neuropa-
thies involve disorders of sympathetic and parasympa-
thetic nervous system function. There may be disorders
of vasomotor function, decreased cardiac responses,
inability to empty the bladder, gastrointestinal motility
problems, and sexual dysfunction.
54
Defects in vaso-
motor reflexes can lead to dizziness and syncope due
to postural hypotension when the person moves from
the supine to the standing position (see Chapter 18).
Incomplete emptying of the bladder predisposes to uri-
nary stasis and bladder infection and increases the risk
of renal complications.
Gastrointestinal motility disorders are common in
persons with long-standing diabetes. The symptoms
vary in severity and include gastroparesis, constipation,
diarrhea, and fecal incontinence. Gastroparesis (delayed
emptying of stomach) is commonly seen in persons with
diabetes.
55
The disorder is characterized by complaints
of epigastric discomfort, nausea, postprandial vomiting,
bloating, and early satiety. Abnormal gastric empty-
ing also jeopardizes the regulation of the blood glucose
level. Diarrhea is another common symptom seen mostly
in persons with poorly controlled type 1 diabetes and
autonomic neuropathy.
56
The pathogenesis is thought to
be multifactorial. Diabetic diarrhea is typically intermit-
tent, watery, painless, and nocturnal and may be associ-
ated with fecal incontinence.
In the male, disruption of sensory and autonomic ner-
vous system function may cause sexual dysfunction (see
Chapter 39). Diabetes is the leading pathophysiological
cause of erectile dysfunction (ED), and it occurs in both
type 1 and type 2 diabetes. Of the 13 million men with
diabetes in the United States, 30% to 60% have ED.
54
Diabetic Nephropathies
Diabetic nephropathy
, a term used to describe the com-
bination of lesions that occur concurrently in the diabetic
kidney, is the leading cause of chronic kidney disease
(CKD) in persons starting renal replacement therapy
(see Chapter 26).
57
Not all people with diabetes develop
clinically significant nephropathy; for this reason, atten-
tion is focused on risk factors for the development of
this complication. Among the suggested risk factors are
genetic and familial predisposition, elevated blood pres-
sure, poor glycemic control, smoking, hyperlipidemia,
and increased albumin excretion.
11,58
Diabetic nephrop-
athy occurs in family clusters, suggesting a familial
predisposition, although this does not exclude the pos-
sibility of environmental factors shared by siblings.
The risk for development of kidney disease is greater
among Native Americans, Hispanic Americans (espe-
cially Mexican Americans), and African Americans.
11,58
The most common kidney lesions in people with dia-
betes are those that affect the glomeruli. These include
capillary basement membrane thickening, diffuse glo-
merular sclerosis, and nodular glomerulosclerosis, in
which the development of nodular lesions in the glomer-
ular capillaries causes impaired blood flow with progres-
sive loss of kidney function and, eventually, renal failure
(see Chapter 25). Nodular glomerulosclerosis is thought
to occur only in people with diabetes. Changes in the
basement membrane in diffuse nodular glomeruloscle-
rosis allow plasma proteins to escape in the urine, caus-
ing albuminuria, hypoalbuminemia, edema, and other
signs of impaired kidney function.
Kidney enlargement, nephron hypertrophy, and
hyperfiltration are early accompaniments of diabetes,
reflecting the increased work performed by the kidneys
in reabsorbing excessive amounts of glucose. One of
the first manifestations of diabetic nephropathy is an
increase in urinary albumin excretion, which is defined
as a urine protein loss greater or equal to 30 mg/day
or an albumin-to-creatinine ratio (A/C ratio) greater
or equal to 30
μ
g/mg (normal <30
μ
g/mg) from a spot
urine collection.
58
It is recommended that the A/C ratio
be the preferred screen for increased urinary albumin
excretion. Both systolic and diastolic forms of hyper-
tension accelerate the progression of diabetic nephrop-
athy. Even moderate lowering of blood pressure can
decrease the risk of CKD.
11
The estimated glomerular
filtration rate (eGFR) should also be monitored on a
regular basis.
Measures to prevent diabetic nephropathy or its pro-
gression in persons with diabetes include achievement of
CHART 33-2
Classification of Diabetic Neuropathies
Somatic
Polyneuropathies (bilateral sensory)
Paresthesias, including numbness and tingling
Impaired pain, temperature, light touch, two-point
discrimination, and vibratory sensation
Decreased ankle and knee-jerk reflexes
Mononeuropathies
Involvement of a mixed nerve trunk that includes
loss of sensation, pain, and motor weakness
Amyotrophy
Associated with muscle weakness, wasting, and
severe pain of muscles in the pelvic girdle and
thigh
Autonomic
Impaired vasomotor function
Postural hypotension
Impaired gastrointestinal function
Gastric atony
Diarrhea, often postprandial and nocturnal
Impaired genitourinary function
Paralytic bladder
Incomplete voiding
Erectile dysfunction
Retrograde ejaculation
Cranial nerve involvement
Extraocular nerve paralysis
Impaired pupillary responses
Impaired special senses
