Resin-induced injury to the gastrointestinal tract (GIT) is a pathological phenomenon that occurs due to the ingestion of certain therapeutic resins. These resins, while medically useful, can result in significant histological changes that need to be accurately identified for appropriate diagnosis and treatment. Three commonly implicated resins include Kayexalate, bile acid sequestrants, and Sevelamer. Understanding the microscopic findings associated with each resin can help pathologists and clinicians manage potential complications.
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1. Kayexalate (Sodium Polystyrene Sulfonate)
Kayexalate is a resin commonly used to treat hyperkalemia, as it binds potassium in the gastrointestinal tract to facilitate its removal from the body. However, its use can lead to damage in the GIT, manifesting with characteristic histopathological findings.
- Key Histological Findings:
- Basophilic crystals: These crystals exhibit distinctive “fish scales” under Hematoxylin and Eosin (H&E) staining. The scales are a defining feature of Kayexalate-induced injury.
- Special stains: Acid-fast bacillus (AFB) staining results in black crystals, while periodic acid-Schiff with diastase (PAS-D) reveals a hot pink coloration, helping distinguish these crystals from other substances.
- Microscopy features: The crystals are irregular, angular, and often embedded within necrotic mucosal tissue.
These findings are crucial in diagnosing Kayexalate-induced injury, as they can mimic other conditions such as ischemic enterocolitis or inflammatory bowel disease.
2. Bile Acid Sequestrants (e.g., Cholestyramine)
Bile acid sequestrants are resins used to lower cholesterol levels and treat bile acid diarrhea by binding bile acids in the intestine. Like Kayexalate, they can also cause histological changes in the GIT.
- Key Histological Findings:
- Orange-black crystals: Unlike Kayexalate, bile acid sequestrants display orange-black crystals under H&E staining. Notably, they lack the “fish scale” pattern seen with Kayexalate.
- Special stains: AFB staining produces yellow crystals, while PAS-D shows a bluish-black hue.
- Microscopy features: The crystals tend to appear amorphous and lack the sharp angularity seen with Kayexalate crystals.
Recognizing bile acid sequestrant crystals is essential, as misinterpretation could lead to unnecessary interventions, considering the benign nature of their presence in the GIT.
3. Sevelamer
Sevelamer is a phosphate-binding resin used in patients with chronic kidney disease to control hyperphosphatemia. This resin, while effective, can lead to gastrointestinal mucosal injury and distinctive crystal deposition.
- Key Histological Findings:
- Broad, curved fish scales: Sevelamer presents with broad, irregularly spaced fish scales under H&E staining. These scales are usually double-toned, with variations in hue between regions of the crystal.
- Special stains: AFB staining produces magenta-colored crystals, while PAS-D staining results in a lavender color.
- Microscopy features: Sevelamer crystals tend to be larger and more irregular than those of Kayexalate or bile acid sequestrants, and they often form a layered or lamellar pattern within the mucosa.
Due to the potential for Sevelamer-induced ulcerations, early recognition of these crystals can help guide management and avoid further injury.
Summary of Key histologic findings
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