Modul DIARE DAN KONSTIPASI

DIARE DAN KONSTIPASI

FUNGSI NORMAL GASTROINTESTINAL

Absorbsi Cairan Dan Elektrolit

Jumlah cairan yang terdapat di dalam saluran gastrointestinal kira-kira 8-10 L/hari,termasuk 2 L/hari yang berasal dari makanan,sebagian besar diabsorbsi di usus halus.Absorbsi di colon normalnya sebesar 0,05-2 L/hari dengan kapasitas sebesar 6 L/hari jika diperlukan.Absorbsi air terjadi secara pasif mengikuti transport aktif Na+,Cl-,glukosa dan garam empedu.Mekanisme transport lainnya adalah pertukaran Cl-/HCO3-,pertukaran Na+/H+,sekresi H+,K+,Cl- dan HCO3-,kotransport Na+-glukosa dan transport aktif Na+ menembus membran basolateral dengan pompa Na+,K+-ATPase.

 

Absorbsi Nutrient

1.Usus halus bagian proximal : besi,kalsium,folat,lemak(setelah trigliserida dihidrolisis menjadi asam lemak oleh enzim lipase pancreas dan colipase ),protein(setelah dihidrolisis oleh peptidase pancreas dan usus),karbohidrat(setelah dihidrolisis oleh amilase dan disakaridase) ; triglesrida diabsorbsi dalam bentuk micelles setelah dilarutkan oleh garam empedu ; asam amino dan dipeptida diabsorbsi lewat carrier spesifik ; gula diabsorbsi melalui transport aktif.

2. Usus halus bagian distal : vitamin B 12,garam empedu dan air.

3. Colon : air dan elektrolit.

 

Motilitas Usus

Menyebabkan pergerakan propulsi dari lambung sampai anus dan pemisahan komponen untuk proses absorbsi nutrien.Propulsi dikontrol melalui mekanisme neural,miogenik dan hormonal.Motilitas colon berupa peristaltic local untuk mengeluarkan feses.Defekasi terjadi akibat relaksasi sfingter anal internal akibat respon dari distensi rectum dengan sfingter anal eksternal yang diatur secara volunteer.

DIARE

Fisiologi

Diare didefinisikan sebagai pengeluaran feses dalam jumlah berlebih >200 g/hari atau konsistensinya yang lebih cair.Ada 5 mekanisme yang menyebabkan diare :

1.Diare Osmotik

     Zat yang tidak dapat diabsorbsi akan meningkatkan tekanan intraluminal,menyebabkan   pengeluaran air,biasanya akan berhenti dengan puasa,osmolal gap feses >40.Penyebabnya antara lain defisiensi disakaridase(lactase),insufisiensi pancreas,pertumbuhan berlebihan bakteri,penggunaan laktulosa atau sorbitol,penggunaan laxarive polyvalent,celiac atau tropical sprue dan short bowel syndrome.Defisiensi lactase dapat terjadi primer atau sekunder(akibat gastroenteritis viral,bakteri,protozoa,celiac atau tropical sprue,atau kwashiorkor)

2.Diare Sekretorik

     Sekresi ion aktif akan menyebabkan pengeluaran air ; diare bersifat cair,jumlah sangat banyak,tidak dipengaruhi oleh puasa ; Na+ dan K+ feses meningkat dengan osmolal gap <40.Penyebabnya meliputi infeksi virus (Rota virus,Norwalk virus),infeksi bakteri(Cholera,E.Colienterotoxigenic,Staphylococcusaureus),protozoa(Giardia,Isospora,Cryptosporidium),AIDS(mikobakterium),obat(teofilin,colchicines,prostaglandin,diuretic),Zollinger-Ellison syndrome,VIP producing timors,carcinoid tumor(histamin dan serotonin)carcinoma thyroid medulla(prostaglandin dan calcitonin),sistemik mastocytosis,basofilik leukemia,adenoma villous colon distal(sekresi cairan kaya K+),colitis kolagen dan mikroskopis dan diare cholerrheic(malabsorbsi garam empedu).

3.Diare Exudatative

     Mukosa colon mengalami inflamasi,nekrosis akibat pelepasan prostaglandin oleh sel inflammatory,feses biasanya mengandung PMN lekosit dan darah.Penyebabnya adalah infeksi bakteri,parasit,Crohn’s disease,ulcerative proctocolitis,inflammatroty bowel disease,enterocolitis radiasi,khemotherapi cancer,iskemia intestinal.

4.Gangguan Motilitas Usus

      Diare umumnya bersifat intermitten dan diselingi dengan konstipasi.Penyebabnya meliputi diabetes mellitus,insufisiensi adrenal,hipertiroid,penyakit kolagen-vascular,infestasi parasit,gastrin dan keadaan hipersekresi VIP,amyloidosis,laxative(mengandung magnesium),antibiotik(eritromisin),obat antikolinergik,penyakit saraf(Parkinson,neuropati traumatic),fecolith,penyakit divertikular,dan irritable bowel syndrome.Darah di dalam saluran cerna akan bersifat seperti laxative sehingga akan menyebabkan diare oleh karena peningkatan motilitas.

5.Penurunan permukaan absorbsi

     Umumnya akibat manipulasi bedah(reseksi usus yang luas) sehingga mengakibatkan gangguan absorbsi lemak,karbohidrat,air dan elektrolit.Dapat pula bersifat spontan apabila terdapat fistula enteroenteric(gastrocolic).   

Evaluasi         

Riwayat penyakit

     Diare perlu dibedakan dengan inkontinensia fecal,perlu ditanyakan adanya perubahan kaliber feses,perdarahan rectal dan apakah ada feses yang kecil-kecil .Diare dan konstipasi yang timbul berselingan menandakan adanya suatu obstruksi colon (carcinoma) atau suatu irritable bowel syndrome.Perjalanan penyakit yang tiba-tiba dan akut disertai dengan mual,muntah dan demam biasanya merupakan suatu infeksi bakteri atau virus,divertikulitis,iskemia,enterocolitis radiasi,drug induce diare dan tanda awal dari inflammatory bowel disease.>90% diare akut adalah disebabkan oleh infeksi.Perjalanan penyakit yang lebih lama (>4 minggu) biasanya merupakan suatu keadaan malabsorbsi,inflammatory bowel disease,gangguan metabolic atau endokrin,insufisiensi pancreas,penggunaan laxative,iskemia,keganasan atau irritable bowel syndrome.Parasit dan bentuk tertentu enteritis bakteri  dapat pula menyebabkan suatu keluhan yang kronis.Feses yang berbau busuk atau berminyak menunjukkan kemungkinan adanya malabsorbsi lemak.Fecolith dapat memberikan gambaran diare oleh karena hanya zat cair saja yang dapat melewati obstruksi pertial tersebut.Ada beberapa agent yang biasanya menyebabkan diare pada penderita immunocomprimised (AIDS).

Pemeriksaan Fisik      

     Tanda dehidrasi sering terdapat pada diare akut yang berat. Demam dan nyeri abdomen menandakan adanya infeksi atau inflamasi tetapi sering tidak ada apabila penyebabnya adalah virus.Adanya malnutrisi merupakan bukti bahwa proses bersifat kronis.Tanda-tanda defisiensi vitamin menandakan adanya malabsorbsi (cheilosis akibat defisiensi riboflavin atau besi,glossitis akibat defisiensi B12,folat).

Pemeriksaan Feses                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          

     Kultur,lekosit,toxin C.difficile,parasit dan telurnya merupakan pemeriksaan yang penting.Adanya darah dan lekosit menandakan suatu proses inflamasi (colitis ulserative,Crohn’s disease,infeksi atau iskemia.Pewarnaan gram sering menemukan Stafilokokus,Campylobacter atau Candida.Steatorrhea (dengan pewarnaan Sudan III) menandakan adanya malabsorbsi atau insufisiensi pancreas.Pengukuran kadar Na+ dan K+ dapat membedakan diare osmotic dengan diare lainnya;pada diare osmotic osmolal gap feses >40 dimana osmolal gap = osmol serum – ( 2x (Na+K)feses )

Pemeriksaan Laboratorium

     Pemeriksaan darah lengkap dapat menunjukkan adanya anemia (perdarahan akut atau kronis,malabsorbsi besi,folat atau B12),lekositosis (inflamasi),eosinofilia (parasit,neoplasma dan inflammatory bowel diseases).Kadar serum kalsium,albumin,besi,kolesterol,folat,B12,vitamin D dan karoten ; serum iron binding capacity ; protrombin time dapat meberikan bukti adanya malabsorbsi atau maldigesti

 

Pemeriksaan Lain

     Test absorbsi D-Xylose digunakan untuk menilai fungsi absorbsi usus halus.Biopsi usus halus sangat berguna untuk evaluasi malabsorbsi usus.Pemeriksaan khusus lainnya antara lain Schilling test (malabsorbsi B12),lactose H2 breath (malabsorbsi karbohidrat),14C xylose da lactulose H2 breath test (pertumbuhan bakteri yang berlebihan),glycocholic breath test (malabsorbsi ileum),triolein breath test (malabsorbsi lemak) dan bentiromide dan secretin test (insufisiensi pancreas).Sigmoidoscopy dan colonoscopy dengan biopsy sangat berguna untuk diagnosis colitis (pseudomembranous,iskemia,mikroskopik) ; tetapi tidak dapat membedakan antara infeksi dan noninfeksi colitis (idiopatik ulcerative).Kontras barium dapat memperkirakan adanya malabsorbsi (lipatan usus yang tebal),inflammatory disease (ileitis atau colitis),tuberculosis (inflamasi ileocecal),neoplasma,intestinal fistula atau gangguan motilitas.

 

Pengobatan

     Pendekatan terapi untuk diare akut dan kronis dapat dilihat pada gambar di bawah ini.Terapi simptomatik meliputi rehidrasi,penggantian elektrolit,zat pengikat secara osmotic (kaolin-pektin) dan opiat untuk menurunkan motilitas usus (loperamide,diphenoxylate) ; opiat merupakan kontra indikasi pada kasus diare karena infeksi atau inflamasi.

 

 

MALABSORBSI SINDROM

     Malabsorbsi zat nutrien dapat menyebabkan diare osmotic,steatorrhea atau defisiensi spesifik (besi,folat,B12,vitamin A,D,E,K).Penyebabnya dapat dilihat pada tabel di bawah ini.Protein-losing enteropathy bisa akibat dari berbagai macam malabsorbsi ; hal ini berhubungan dengan hipoalbuminemia dan dapat dideteksi dengan memeriksa alfa1 antitripsin feses dan kadar albumin radiolabel.Terapi ditujukan terhadap penyakit dasarnya.

KONSTIPASI

     Didefinisikan sebagai berkurangnya frekuensi defekasi menjadi <1 per minggu atau kesulitan dalam defekasi ; bisa mengakibatkan nyeri abdomen,distensi dan fekolith sampai terjadinya obstruksi bahkan perforasi.Faktor-faktor ikutan yang sering adalah inaktivitas,diet rendah serat dan tidak adanya waktu yang sesuai untuk defekasi.

 

Penyebab Khusus

     Gangguan motilitas kolon akibat disfungsi neurologis (diabetes mellitus,trauma medulla spinalis,multiple sclerosis,penyakit Chagas,Hirschsprung disease,chronic idiopatic intestinal pseudoobstruction,idiopatic megacolon),scleroderma,obat-obatan (antikolinergik,opiat,antasid alumunium atau kalsium,antagonis kalsium,suplemen besi,sukralfat),hipotiroidism,Cushing’s syndrome,hipokalemia,hiperkalsemia,dehidrasi,penyebab mekanik (tumor kolorektal,diverticulitis,volvulus,hernia,intussusception) dan nyeri anorektal (fissura,hemorrhoid,abses atau proktitis) menyebabkan retensi,konstipasi dan fecolith.

 

Pengobatan

     Apabila tidak ada penyebab khusus,konstipasi dapat berkurang dengan jalan edukasi,latihan,diet tinggi serat,zat bulking (psyllium) dan meningkatkan intake air.Terapi spesifik meliputi penanganan obstruksinya (fecolith,tumor),penghentian obat hipomotilitas (antasid alumunium atau calcium,opiat).Untuk terapi simptomatik dapat dipakai agent yang mengandung magnesium atau katartik lainya.Hipomotilitas atau dismotiliti berat karena opiat dapat digunakan zat yang aktif secara osmotic (oral lactulose,intestinal polyethylene glycol) dan oral atau rectal emollient laxative (garam docusate) dan minyak mineral.

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