Acute & Chronic gout

Content

•       Acute gout

•       Uric
acid nephrolithiasis

•       Chronic gout

OBJECTIVE

At the
end of the class the students will be able to

•       Explain acute gout

•       Briefly explain clinical
presentation of acute gouty arthritis and uric acid nephrolithiasis

Gout

•       Gout is diagnosed clinically by
symptoms rather than laboratory tests of uric acid.

•       In fact, asymptomatic hyperuricemia
discovered incidentally generally requires no therapy because many individuals
with hyperuricemia will never experience an attack of gout.

•       These patients should still be
encouraged to implement lifestyle measures to reduce serum urate
concentrations.

Clinical Presentation

ACUTE GOUTY ARTHRITIS

•       A classic acute attack of gouty
arthritis is characterized by rapid and localized onset of excruciating pain,
swelling, and inflammation.

•       The attack is typically monarticular
at first, most often affecting the first metatarsophalangeal joint (great toe)
and then, in order of frequency, the insteps, ankles, heels, knees, wrists,
fingers, and elbows.

•       In one half of initial attacks, the
first metatarsophalangeal joint is affected, a condition commonly referred to
as podagra.

Clinical
Manifestations of Gout

•       Up to 90% of patients with gout will
experience podagra at some point in the course of their disease.

•       Atypical presentations of gout also
occur. For elderly patients, gout can present as a chronic polyarticular
arthritis that can be confused with rheumatoid arthritis or osteoarthritis.

•       Additionally, theonset of gout may
be less dramatic than the typical acute attack and have fewer clinical
findings.

•       Multiple small joints in the hands
may be involved, especially in elderly women.

•       The predilection of acute gout for
peripheral joints of the lower extremity is probably related to the low
temperature of these joints combined with high intraarticular urate
concentration.

•       Synovial effusions are likely to
occur transiently in weight-bearing joints during the course of a day with
routine activity.

•       At night, water is reabsorbed from
the joint space, leaving behind a supersaturated solution of monosodium urate,
which can precipitate attacks of acute arthritis.

•       Attacks generally begin at night
with the patient awakened from sleep by excruciating pain.

•       The development of crystal-induced
inflammation involves a number of chemical mediators causing vasodilation,
increased vascular permeability, complement activation, and chemotactic
activity for polymorphonuclear leukocytes.

•       Phagocytosis of urate crystals by
the leukocytes results in rapid lysis of cells and a discharge of lysosomal and
proteolytic enzymes into the cytoplasm.

•       The ensuing inflammatory reaction is
associated with intense joint pain, erythema, warmth, and swelling. Fever is
common, as is leukocytosis.

•       Untreated attacks may last from 3 to
14 days before spontaneous recovery.

•       Although acute attacks of gouty
arthritis may occur without apparent provocation, a number of conditions may
precipitate an attack.

•       These include stress, trauma,
alcohol ingestion, infection,surgery, rapid lowering of serum uric acid by
ingestion of uric acid-lowering agents.

•       Other crystal-induced arthropathies
that may resemble gout on Clinical Presentationare caused by calcium pyrophosphate
dihydrate crystals(pseudogout) and calcium hydroxyapatite crystals, which are
associated with calcific periarthritis, tendinitis, and arthritis.

•       Acute flares of gouty arthritis may
occur infrequently, but over time the interval between attacks may shorten if
appropriate measures to correct hyperuricemia are not undertaken.

•       Later in the disease, tophaceous
deposits of monosodium urate crystals in the skin or subcutaneous tissues may
be found.

•       These tophi can be anywhere but are
often found on the hands, wrists, elbows, or knees.

•       It is estimated to take 10 or more
years for tophi to develop.

Diagnostic Evaluation of Gout

•       A definitive diagnosis of gout
requires aspiration of synovial fluid from the affected joint and
identification of intracellular crystals of monosodium urate monohydrate in
synovial fluid leukocytes.

•       Identification of monosodium urate
crystals is highly dependent on the experience of the observer.

•       Crystals are needle shaped, and when
examined under polarizing light microscopy, they are strongly negatively
birefringent.

•       Crystals can be observed in synovial
fluid during asymptomatic periods.

•       If an affected joint is tapped, the
resulting synovial fluid may have white cells and appear purulent. Such
findings should always raise the question of infection.

•       If any clinical features of
infection are present, such as high fever, elevated white blood cell count,
multiple joints affected, or an identified source of infection, proper
diagnosis and treatment are critical.

•       Patients with gout can have septic
arthritis. Diabetes, alcohol abuse, and advanced age increase the likelihood of
septic arthritis.

•       In lieu of obtaining a synovial
fluid sample from an affected joint to inspect for urate crystals, the clinical
triad of inflammatory monoarthritis, elevated serum uric acid level, and
response to colchicine can be used to diagnose gout.

•       This approach has limitations,
including a failure to recognize atypical gout presentations and the fact that
serum uric acid levels can be normal or even low during an acute gout attack.

•       In addition, use of colchicine as a
diagnostic tool for gout is limited by lack of sensitivity and specificity for
the disease.

•       Other conditions such as psoriatic
arthritis, sarcoidosis, and Mediterranean fever can respond to colchicine therapy.

•       For patients with long-standing
gout, radiographs may show punched-out marginal erosions and secondary
osteoarthritic changes; however, in an acute first attack radiographs will be
unremarkable.

•       The presence of chondrocalcinosis on
radiographs may indicate pseudogout.

•       Some studies have recently examined
the use of magnetic resonance imaging and computed tomography to obtain images
for patients with gout; however, this is not currently considered part of
normal practice.

URIC ACID NEPHROLITHIASIS

•       Clinicians should be suspicious of
hyperuricemic states for patients who present with kidney stones, as
nephrolithiasis occurs in 10% to 25% of patients with gout.

•       The frequency of urolithiasis
depends on serum uric acid concentrations, acidity of the urine, and urinary
uric acid concentration.

•       Typically, patients with uric acid
nephrolithiasis have a urinary pH of less than 6.0.

•       Uric acid has a negative logarithm
of the acid ionization constant of 5.5.

•       Therefore, when the urine is acidic,
uric acid exists primarily in the unionized, less soluble form.

•       At a urine pH of 5.0, urine is
saturated at a uric acid level of 15 mg/ dL (0.89 mmol/L).

•       When the urine pH is 7.0, the
solubility of uric acid in urine is increased to 200 mg/dL (11.9 mmol/L).

•       For patients with uric acid
nephrolithiasis, urinary pH typically is less than 6.0 and frequently less than
5.5.

•       When acidic urine is saturated with
uric acid, spontaneous precipitation of stones may occur.

•       Other factors that predispose
individuals to uric acid nephrolithiasis include excessive urinary excretion of
uric acid and highly concentrated urine.

•       The risk of renal calculi approaches
50% in individuals whose renal excretion of uric acid exceeds 1,100 mg/ day
(6.5 mmol/day).

•       In addition to pure uric acid
stones, hyperuricosuric individuals are at increased risk for mixed uric
acid–calcium oxalate stones and pure calcium oxalate stones.

•       Uric acid stones are usually small,
round, and radiolucent.

•       Uric acid stones containing calcium
are radiopaque.

GOUTY NEPHROPATHY

•       There are two types of gouty
nephropathy: acute uric acid nephropathy and chronic urate nephropathy.

•       In acute uric acid nephropathy,
acute renal failure occurs as a result of blockage of urine flow secondary to
massive precipitation of uric acid crystals in the collecting ducts and
ureters.

•       This syndrome is a well-recognized
complication for patients with myeloproliferative or lymphoproliferative
disorders and is a result of massive malignant cell turnover, particularly
after initiation of chemotherapy.

•       Chronic urate nephropathy is caused
by the long-term deposition of urate crystals in the renal parenchyma.

•       Microtophi may form, with a
surrounding giant-cell inflammatory reaction.

•       A decrease in the kidneys’ ability
to concentrate urine and the presence of proteinuria may be the earliest
pathophysiologic disturbances.

•       Hypertension and nephrosclerosis are
common associated findings.

•       Although renal failure occurs in a
higher percentage of gouty patients than expected, it is not clear if hyperuricemia
per se has a harmful effect on the kidneys.

•       The chronic renal impairment seen in
individuals with gout may result largely from the coexistence of hypertension,
diabetes mellitus, and atherosclerosis.

TOPHACEOUS GOUT

•       Tophi (urate deposits) are uncommon
in the general population of gouty subjects and are a late complication of
hyperuricemia.

•       The most common sites of tophaceous
deposits for patients with recurrent acute gouty arthritis are the base of the
great toe, helix of the ear, olecranon bursae, Achilles tendon, knees, wrists,
and hands

•       Eventually, even the hips,
shoulders, and spine may be affected.

•       In addition to causing obvious
deformities, tophi may damage surrounding soft tissue, cause joint destruction
and pain, and even lead to nerve compression syndromes including carpal tunnel
syndrome.

Summary

•       Gout
is different from hyperuricemia

ACUTE GOUTY ARTHRITIS

•       A classic acute attack of gouty
arthritis is characterized by rapid and localized onset of excruciating pain,
swelling, and inflammation

URIC ACID NEPHROLITHIASIS

The
frequency of urolithiasis depends on serum uric acid concentrations, acidity of
the urine, and urinary uric acid concentration

 TOPHACEOUS GOUT

•       Tophi (urate deposits) are uncommon
in the general population of gouty subjects and are a late complication of
hyperuricemia