/visulize Calots triangle And its borders with labels

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Calot's Triangle (Hepatocystic Triangle)

Original Description (Calot, 1891)

Calot originally described the triangle as bounded by:

Border	Structure
Inferior	Cystic duct
Medial	Common hepatic duct (CHD)
Superior	Cystic artery

Modern / Contemporary Definition (Hepatocystic Triangle)

The current surgical working definition is larger and more practical:

Border	Structure
Inferior / Lateral	Cystic duct + medial wall of gallbladder
Medial	Common hepatic duct
Superior	Inferior surface of the liver (segment V)

The cystic artery now lies within (not forming the border of) this triangle - making it the primary target structure to identify safely.

Contents of Calot's Triangle

Cystic artery (branch of the right hepatic artery, typically)
Cystic lymph node (Lund's node / sentinel node) - lies superficial to the cystic artery and acts as a useful intraoperative landmark
Occasionally: an aberrant right hepatic artery or accessory ducts

Diagram 1 - Hepatocystic Triangle (normal anatomy, variant A = green shaded)

Calot's triangle variants - hepatocystic triangle shown in green (A)

Fig. 57.7 from Mulholland & Greenfield's Surgery, 7e - The modern Calot's (hepatocystic) triangle is highlighted in green in panel A. Panels B-F show cystic artery variations.

Diagram 2 - Gallbladder & Bile Duct Arterial Anatomy

Gallbladder and bile duct anatomy with labeled arterial tree

Fig. 71.1 from Bailey & Love's Surgery, 28e - Full arterial labeling: right/left hepatic arteries, cystic artery, right/left choledochal arteries, hepatic, retroduodenal, and gastroduodenal arteries.

Diagram 3 - Hepatocystic Triangle with Anatomical Variations

Hepatocystic triangle with variants: normal (a), caterpillar turn (b), tortuous right hepatic artery (c)

Fig. 71.2 from Bailey & Love's Surgery, 28e - (a) Normal hepatocystic triangle (white lines = triangle borders); (b) tortuous common hepatic artery; (c) tortuous right hepatic artery with short cystic artery - the "caterpillar turn" / Moynihan's hump.

Surgical Significance

Critical View of Safety (CVS) - The triangle must be fully dissected during laparoscopic cholecystectomy so that only two structures (cystic duct + cystic artery) are seen entering the gallbladder before clipping.
Biliary injury risk - The CBD lies below/dorsal to the triangle. The R4U line (Rouvière's sulcus → segment IV → umbilical fissure) is a safety reference: cystic duct and artery lie ventral to this line; CBD lies below it.
Cystic artery variations - In 15% of cases the right hepatic artery or cystic artery crosses anterior to the CHD and cystic duct, increasing injury risk. Six recognized variants are shown in the first diagram above.

Sources: Mulholland & Greenfield's Surgery, 7e (§57); Bailey & Love's Short Practice of Surgery, 28e (§71); Maingot's Abdominal Operations.

/visulize Colitis

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I now have all four key images. I have everything I need to deliver a comprehensive, well-visualized comparison of the three types of colitis.

Colitis - Gross/Macroscopic Anatomy & Distribution

1. ULCERATIVE COLITIS (UC)

Distribution: Starts in the rectum, spreads continuously and proximally - never skips. Confined to the colon only.

Feature	UC
GI tract involvement	Colon + rectum only
Pattern	Continuous, no skip lesions
Wall depth	Mucosal & submucosal only (not transmural)
Ulcers	Superficial, broad-based
Characteristic lesion	Pseudopolyps (regenerating mucosa bulging into lumen)
Strictures	Rare
Fistulae	No
Perianal disease	No

Extent subtypes (Montreal Classification):

Proctitis - rectum only
Left-sided colitis - up to splenic flexure
Pancolitis - entire colon

2. CROHN'S COLITIS

Distribution: Can involve any part of the GI tract from mouth to anus. Skip lesions are the hallmark - discontinuous inflamed segments with normal bowel between them. Terminal ileum is affected in ~70%.

Feature	Crohn's
GI tract involvement	Mouth to anus (esophagus to anus)
Pattern	Skip lesions
Wall depth	Transmural (full thickness)
Ulcers	Deep, knife-like / "cobblestoning"
Characteristic lesion	Creeping fat, strictures, fistulae
Granulomas	Yes (~35%)
Fistulae / sinuses	Yes
Perianal disease	Yes

Diagram 1 - Disease Distribution Comparison (Lippincott)

Crohn's disease vs Ulcerative Colitis - distribution patterns showing skip lesions vs continuous rectal involvement

Fig. 42.15 from Lippincott Illustrated Reviews: Pharmacology - (A) Crohn's disease with skip lesions involving terminal ileum and colon segments; (B) Ulcerative colitis beginning at rectum with continuous proximal spread.

Diagram 2 - Gross & Wall-Layer Distribution (Robbins Pathology)

Robbins: Crohn disease vs Ulcerative Colitis - macroscopic distribution and transmural vs mucosal cross-section comparison

Fig. 17.35 from Robbins, Cotran & Kumar Pathologic Basis of Disease - Left column = gross distribution map; Right column = cross-section of bowel wall showing depth of inflammation for each condition.

Key wall-layer takeaways from the diagram:

Crohn's (top): transmural inflammation + fissures + creeping fat + thickened wall
UC (bottom): mucosal/submucosal inflammation + pseudopolyps + broad-based ulcers, wall thickness normal

3. ISCHEMIC COLITIS

Distribution: Affects watershed zones - areas where two major arterial territories meet and collateral flow is weakest:

Watershed Zone	Location	Eponym
#1 (most common)	Splenic flexure	Griffiths' point
#2	Rectosigmoid junction	Sudeck's point
#3 (embolic)	Right colon (cecum/ascending)	Terminal branch of SMA (ileocolic)

The rectum is usually spared - it has dual supply from both IMA and iliac circulations.

Collateral vessels:

Marginal artery of Drummond - runs parallel to colon, absent at splenic flexure in up to 18% of people
Arc of Riolan - connects SMA and IMA closer to the mesenteric root; its presence often signals a proximal major vessel obstruction

Diagram 3 - Ischemic Colitis Watershed Zones (Sabiston Surgery)

Ischemic colitis watershed zones - gray shaded areas show splenic flexure (Griffiths), right colon, and rectosigmoid (Sudeck's point) vulnerability

Fig. 95.54 from Sabiston Textbook of Surgery - Gray dashed regions = ischemia-vulnerable watershed areas: splenic flexure (top-right), right colon/cecum (bottom-left), and rectosigmoid (bottom-center). All major colic arteries labeled.

Diagram 4 - Arc of Riolan Collateral Anatomy (Sabiston Surgery)

Arc of Riolan connecting SMA and IMA with labeled middle colic and superior mesenteric arteries

Fig. 95.53 from Sabiston Textbook of Surgery - The Arc of Riolan (meandering mesenteric artery) bridges SMA and IMA territories; a prominent arc is a clue to proximal major vessel occlusion.

Side-by-Side Summary

Feature	Ulcerative Colitis	Crohn's Colitis	Ischemic Colitis
Location	Colon only	Any part of GI tract	Colon (watershed zones)
Pattern	Continuous from rectum	Skip lesions	Focal (splenic flexure, rectosigmoid, right colon)
Rectum	Always involved	Often spared	Usually spared
Wall depth	Mucosa/submucosa	Transmural	Variable (mucosal → full thickness necrosis)
Mechanism	Autoimmune	Autoimmune	Ischemia / hypoperfusion
Fistulae	No	Yes	No
Age predilection	20-40 years	15-30 years	Elderly (>60 years)

Sources: Robbins Pathologic Basis of Disease; Sabiston Textbook of Surgery, 21e; Lippincott Illustrated Reviews: Pharmacology; Goldman-Cecil Medicine, International Edition.

Colitis

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Colitis - Overview & Types

Colitis is inflammation of the large intestine (colon). It is not a single disease - it is a pattern of injury that can result from autoimmune, ischemic, infectious, or idiopathic causes. The key to management is identifying the underlying type.

Major Types at a Glance

Type	Cause	Location	Key Feature
Ulcerative Colitis	Autoimmune	Rectum → continuous proximal spread	Mucosal only, bloody diarrhea
Crohn's Colitis	Autoimmune	Any GI segment, skip lesions	Transmural, fistulae, strictures
Ischemic Colitis	Vascular / low flow	Watershed zones (splenic flexure, rectosigmoid)	Rectum spared, elderly
Infectious Colitis	Bacteria, parasites (C. diff, E. coli, Shigella)	Variable	Acute onset, often self-limiting
Microscopic Colitis	Idiopathic / autoimmune	Right colon predominant	Normal endoscopy, watery diarrhea

1. Ulcerative Colitis (UC)

Distribution: Starts always in the rectum, spreads continuously and proximally. Colon only - never involves the small bowel.
Extent subtypes (Montreal Classification): Proctitis (rectum only) → Left-sided (to splenic flexure) → Pancolitis (entire colon)
Wall involvement: Mucosa and submucosa only - NOT transmural
Gross features: Granular/erythematous mucosa, superficial broad-based ulcers, pseudopolyps (islands of regenerating mucosa), loss of haustral folds in chronic disease ("lead pipe" colon)
Hallmark symptom: Bloody diarrhea, urgency, tenesmus
Complications: Toxic megacolon, colorectal cancer (risk begins after 7-10 years; ~10% per decade), primary sclerosing cholangitis
Peak age: 20-40 years (second smaller peak after 60)

2. Crohn's Colitis (Crohn's Disease)

Distribution: Mouth to anus - any part of the GI tract. Skip lesions (discontinuous involvement) are the hallmark. Terminal ileum involved in ~70%.
Wall involvement: Transmural (full thickness) - this explains why fistulae and abscesses form
Gross features: Deep "knife-like" fissures and ulcers, cobblestone mucosa, creeping fat (fat wrapping around bowel wall), strictures, thickened wall
Hallmark symptom: Abdominal pain (RLQ), diarrhea (often non-bloody), weight loss, perianal disease
Complications: Fistulae (enteroenteric, enterovesical, enterocutaneous, perianal), abscesses, strictures/obstruction, malabsorption, gallstones, kidney stones
Peak age: 15-30 years (second peak in 7th decade)

Diagram 1 - Distribution Comparison: Crohn's vs UC

Crohn disease vs Ulcerative Colitis - intestinal distribution showing skip lesions (Crohn) vs continuous rectal spread (UC)

Fig. 42.15, Lippincott Illustrated Reviews: Pharmacology - (A) Crohn's: skip lesions throughout small and large bowel including terminal ileum. (B) UC: continuous involvement starting from rectum.

Diagram 2 - Wall Layer Depth (Crohn's vs UC Cross-Section)

Robbins: Crohn disease vs Ulcerative Colitis - gross distribution and bowel wall cross-section showing transmural vs mucosal inflammation

Fig. 17.35, Robbins Pathologic Basis of Disease - Left column: distribution map; Right column: cross-section of bowel wall. Crohn's (top) = transmural inflammation + fissures + creeping fat + thickened wall. UC (bottom) = mucosal/submucosal inflammation + pseudopolyps + broad-based ulcers.

3. Ischemic Colitis

Cause: Insufficient arterial blood supply - usually from low-flow states (heart failure, shock, sepsis), atherosclerosis, or iatrogenic (post-aortic surgery)
Distribution: Watershed zones - areas at the boundary between two major arterial territories:
- Splenic flexure (Griffiths' point) - SMA/IMA border, most common
- Rectosigmoid junction (Sudeck's point) - terminal IMA branches
- Right colon/cecum - vulnerable to embolic SMA occlusion
- Rectum is spared (dual supply from IMA + iliac vessels)
Presentation: Sudden lower abdominal pain, followed within 24 hours by bloody diarrhea; 3 phases - Hyperactive → Paralytic → Shock
Severity: Most cases are mild and self-limiting; 10-20% progress to gangrenous colitis requiring emergency colectomy
Peak age: Elderly (>60 years), more common in women

4. Infectious Colitis

Cause: Bacterial, viral, or parasitic pathogens invading or toxin-producing in the colon
Common organisms:

Organism	Notes
Clostridioides difficile	Most common healthcare-associated colitis; antibiotic-associated; pseudomembranous pattern
Escherichia coli O157:H7	Enterohemorrhagic; hemolytic-uremic syndrome risk
Shigella	Dysentery; invasive mucosa
Campylobacter jejuni	Most common infectious diarrhea worldwide
Entamoeba histolytica	Amebic colitis; "flask-shaped" ulcers
Cytomegalovirus (CMV)	Immunocompromised patients

Presentation: Acute diarrhea (bloody or watery), cramping, fever; usually self-limiting but can mimic IBD or surgical abdomen
Key concern: C. difficile fulminant colitis can cause toxic megacolon and death; it is the most common cause of healthcare-associated diarrhea

5. Microscopic Colitis

Definition: Chronic watery, non-bloody diarrhea with a normal-appearing colon on endoscopy - diagnosed only by biopsy
Two subtypes:
- Collagenous Colitis: Thickened subepithelial collagen band (>10 µm) - pathognomonic finding
- Lymphocytic Colitis: Increased intraepithelial lymphocytes (>20 per 100 surface epithelial cells), no collagen thickening
Distribution: Right colon predominant; rectal sparing in ~8% of cases
Epidemiology: Middle-aged to elderly women (F:M ratio 3:1 to 9:1 for collagenous; slightly lower for lymphocytic); strong association with autoimmune diseases (rheumatoid arthritis, autoimmune thyroiditis, celiac disease); linked to NSAIDs, PPIs, SSRIs, statins
HLA association: Linked to HLA-DQ2 and HLA-DQ1,3, similar to celiac disease
Treatment: Budesonide (most effective), bismuth subsalicylate, cholestyramine; stop offending drugs

Diagram 3 - Microscopic Colitis Histology (Collagenous Colitis)

Microscopic colitis histology - collagenous colitis, rectum vs right colon biopsies showing thickened subepithelial collagen layer

Fig. 5.10, Clinical Gastrointestinal Endoscopy, 3e - Collagenous colitis. A & B: Rectum (low/high power) - minimal involvement. C & D: Right colon (low/high power) - stars mark the thickened subepithelial collagen layer, with increased lamina propria inflammation and surface epithelial detachment.

Distinguishing Features at a Glance

Feature	UC	Crohn's	Ischemic	Infectious	Microscopic
Bloody diarrhea	Yes (common)	Sometimes	Yes (acute)	Sometimes	No
Rectal involvement	Always	Often spared	Spared	Variable	Often spared
Skip lesions	No	Yes	No	No	No
Transmural	No	Yes	Variable	No	No
Fistulae	No	Yes	No	No	No
Normal endoscopy	No	No	No	No	Yes
Cancer risk	Yes (duration-dependent)	Slightly elevated	No	No	No
Age	20-40	15-30	Elderly	Any	Middle-aged women

Sources: Robbins Pathologic Basis of Disease; Sleisenger & Fordtran's GI & Liver Disease; Sabiston Textbook of Surgery, 21e; Lippincott Illustrated Reviews: Pharmacology; Goldman-Cecil Medicine; Clinical Gastrointestinal Endoscopy, 3e.

Create a diagnostic flowchart for colitis workup

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mkdir -p /tmp/workspace/colitis-flowchart && ls /tmp/workspace/colitis-flowchart/

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~/colitis-flowchart/generate_flowchart.py

import matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as plt
import matplotlib.patches as mpatches
from matplotlib.patches import FancyBboxPatch, FancyArrowPatch
import matplotlib.patheffects as pe

fig, ax = plt.subplots(figsize=(22, 32))
ax.set_xlim(0, 22)
ax.set_ylim(0, 32)
ax.axis('off')
fig.patch.set_facecolor('#F7F9FC')

# ── Color palette ────────────────────────────────────────────────────────────
C = {
    'start':    '#1A237E',   # dark navy   – start/end
    'step':     '#1565C0',   # blue        – process step
    'decision': '#E65100',   # orange      – decision diamond
    'lab':      '#2E7D32',   # green       – labs / investigations
    'dx':       '#6A1B9A',   # purple      – final diagnosis boxes
    'tx':       '#00695C',   # teal        – treatment hint
    'arrow':    '#37474F',   # dark grey   – arrows
    'warn':     '#C62828',   # red         – red-flag / urgent
    'bg':       '#FFFFFF',
    'text_lt':  '#FFFFFF',
    'text_dk':  '#1A1A1A',
}

def box(ax, x, y, w, h, text, facecolor, textcolor='white', fontsize=9,
        bold=False, radius=0.4, style='round,pad=0.1', wrap=True):
    patch = FancyBboxPatch((x - w/2, y - h/2), w, h,
                           boxstyle=f"round,pad=0.15",
                           facecolor=facecolor, edgecolor='white',
                           linewidth=1.5, zorder=3)
    ax.add_patch(patch)
    weight = 'bold' if bold else 'normal'
    ax.text(x, y, text, ha='center', va='center', fontsize=fontsize,
            color=textcolor, fontweight=weight, wrap=True,
            multialignment='center', zorder=4,
            bbox=dict(boxstyle='square,pad=0', facecolor='none', edgecolor='none'))

def diamond(ax, x, y, w, h, text, facecolor=None, textcolor='white', fontsize=8.5):
    if facecolor is None:
        facecolor = C['decision']
    dx, dy = w/2, h/2
    pts = [(x, y+dy), (x+dx, y), (x, y-dy), (x-dx, y)]
    polygon = plt.Polygon(pts, closed=True, facecolor=facecolor,
                          edgecolor='white', linewidth=1.5, zorder=3)
    ax.add_patch(polygon)
    ax.text(x, y, text, ha='center', va='center', fontsize=fontsize,
            color=textcolor, fontweight='bold', multialignment='center', zorder=4)

def arrow(ax, x1, y1, x2, y2, label='', color=None):
    if color is None:
        color = C['arrow']
    ax.annotate('', xy=(x2, y2), xytext=(x1, y1),
                arrowprops=dict(arrowstyle='->', color=color,
                                lw=2.0, connectionstyle='arc3,rad=0.0'),
                zorder=2)
    if label:
        mx, my = (x1+x2)/2, (y1+y2)/2
        ax.text(mx+0.15, my, label, fontsize=7.5, color=color,
                fontweight='bold', va='center', zorder=5)

def harrow(ax, x1, y1, x2, y2, label='', color=None):
    """Horizontal-then-vertical arrow via a bend."""
    if color is None:
        color = C['arrow']
    ax.annotate('', xy=(x2, y2), xytext=(x1, y1),
                arrowprops=dict(arrowstyle='->', color=color, lw=1.8,
                                connectionstyle='angle,angleA=0,angleB=90,rad=6'),
                zorder=2)
    if label:
        ax.text((x1+x2)/2, (y1+y2)/2 + 0.15, label, fontsize=7.5, color=color,
                fontweight='bold', ha='center', zorder=5)

# ── Title ─────────────────────────────────────────────────────────────────────
ax.text(11, 31.3, 'COLITIS — DIAGNOSTIC WORKUP FLOWCHART',
        ha='center', va='center', fontsize=16, fontweight='bold',
        color=C['start'],
        bbox=dict(boxstyle='round,pad=0.4', facecolor='#E8EAF6', edgecolor=C['start'], lw=2))

# ══════════════════════════════════════════════════════════════════════════════
# ROW 1  –  Presentation
# ══════════════════════════════════════════════════════════════════════════════
Y1 = 29.5
box(ax, 11, Y1, 9, 0.9,
    'PATIENT PRESENTATION\nDiarrhea ± blood  |  Abdominal pain  |  Urgency / tenesmus',
    C['start'], fontsize=9, bold=True)

arrow(ax, 11, Y1-0.45, 11, Y1-1.15)

# ══════════════════════════════════════════════════════════════════════════════
# ROW 2  –  History & Exam
# ══════════════════════════════════════════════════════════════════════════════
Y2 = 27.9
box(ax, 11, Y2, 14, 1.1,
    'HISTORY & PHYSICAL EXAM\nOnset (acute vs chronic)  |  Blood in stool?  |  Recent antibiotics / NSAIDs / travel\n'
    'Wt loss, fever, fistulae, perianal disease  |  Family history IBD  |  Cardiovascular risk (ischemia)',
    C['step'], fontsize=8.5, bold=False)

arrow(ax, 11, Y2-0.55, 11, Y2-1.3)

# ══════════════════════════════════════════════════════════════════════════════
# ROW 3  –  First branch: Acute vs Chronic
# ══════════════════════════════════════════════════════════════════════════════
Y3 = 26.1
diamond(ax, 11, Y3, 5.5, 1.1,
        'Onset\nACUTE (<3 wks)  or  CHRONIC (>3 wks)?',
        fontsize=8.5)

# ── LEFT branch: ACUTE ────────────────────────────────────────────────────────
harrow(ax, 8.25, Y3, 4.5, Y3, label='ACUTE', color=C['warn'])

Y3L = 26.1
box(ax, 3.0, Y3L, 4.8, 1.2,
    'ACUTE COLITIS WORKUP\n① Stool MC&S (Salmonella, Shigella,\n'
    '   Campylobacter, E.coli O157, Yersinia)\n'
    '② C. difficile toxin PCR (EIA/GDH)\n'
    '③ Ova & Parasites (travel history)\n'
    '④ CBC, CRP, electrolytes, LFTs',
    C['lab'], fontsize=7.5)

arrow(ax, 3.0, Y3L-0.6, 3.0, Y3L-1.45)

Y3La = 24.3
diamond(ax, 3.0, Y3La, 4.2, 0.95,
        'Stool cultures / C. diff\nPOSITIVE?', fontsize=8)

arrow(ax, 3.0, Y3La-0.47, 3.0, Y3La-1.1, label='YES')

box(ax, 3.0, 22.8, 4.2, 0.85,
    '⚕ INFECTIOUS COLITIS\nTargeted antimicrobial / supportive Rx',
    C['dx'], fontsize=8, bold=True)

# "No" from acute → proceeds to chronic workup
harrow(ax, 5.1, Y3La, 8.0, Y3La-1.0, label='NO → proceed\nas chronic', color='#37474F')


# ── RIGHT branch: CHRONIC ─────────────────────────────────────────────────────
harrow(ax, 13.75, Y3, 17.5, Y3, label='CHRONIC', color=C['step'])

Y3R = 26.1
box(ax, 19.0, Y3R, 4.8, 1.2,
    '⚠ RED FLAGS → URGENT\n• Bloody diarrhea + fever + tachycardia\n'
    '• Toxic megacolon (distension, peritonism)\n'
    '• Haemodynamic instability\n→ Admit, IV fluids, urgent imaging',
    C['warn'], fontsize=7.5)

# ══════════════════════════════════════════════════════════════════════════════
# ROW 4  –  Initial Labs (chronic / after excluding infection)
# ══════════════════════════════════════════════════════════════════════════════
Y4 = 24.1
arrow(ax, 11, Y3-0.55, 11, Y4+0.55)   # centre arrow from diamond down

box(ax, 11, Y4, 14, 1.1,
    'INITIAL INVESTIGATIONS\n'
    'Bloods: CBC  |  CRP / ESR  |  CMP (albumin, LFTs, creatinine)  |  Iron studies  |  B12 / Folate  |  TFTs\n'
    'Stool: Fecal calprotectin  |  C. diff PCR  |  MC&S  |  Ova & Parasites',
    C['lab'], fontsize=8.5)

arrow(ax, 11, Y4-0.55, 11, Y4-1.3)

# ══════════════════════════════════════════════════════════════════════════════
# ROW 5  –  Fecal Calprotectin branch
# ══════════════════════════════════════════════════════════════════════════════
Y5 = 22.4
diamond(ax, 11, Y5, 6.0, 1.1,
        'Fecal Calprotectin\n< 50 µg/g  or  ≥ 50 µg/g?', fontsize=8.5)

# Low calprotectin → left
harrow(ax, 8.0, Y5, 4.5, Y5, label='< 50', color=C['tx'])
box(ax, 3.0, Y5, 4.0, 0.85,
    'IBD unlikely\nConsider IBS / functional disorder\nReview & reassess if symptoms persist',
    C['tx'], fontsize=7.5)

# High calprotectin → continue
arrow(ax, 11, Y5-0.55, 11, Y5-1.2, label='≥ 50', color=C['decision'])

# ══════════════════════════════════════════════════════════════════════════════
# ROW 6  –  Serology
# ══════════════════════════════════════════════════════════════════════════════
Y6 = 20.9
box(ax, 11, Y6, 13, 0.95,
    'SEROLOGY  (to help differentiate IBD subtypes)\n'
    'pANCA  (UC positive ~60-70%)  |  ASCA IgG/IgA  (Crohn positive ~50-60%)  |  Anti-OmpC  |  Anti-CBir1',
    C['lab'], fontsize=8.5)

arrow(ax, 11, Y6-0.47, 11, Y6-1.2)

# ══════════════════════════════════════════════════════════════════════════════
# ROW 7  –  Colonoscopy branch
# ══════════════════════════════════════════════════════════════════════════════
Y7 = 19.3
box(ax, 11, Y7, 13, 1.0,
    'COLONOSCOPY + ILEOSCOPY WITH BIOPSY  (gold standard)\n'
    'Note: extent & pattern of inflammation  |  mucosal appearance  |  multiple biopsies ≥6 sites',
    C['step'], fontsize=8.5, bold=True)

arrow(ax, 11, Y7-0.5, 11, Y7-1.25)

# ══════════════════════════════════════════════════════════════════════════════
# ROW 8  –  Endoscopic findings branch (3 columns)
# ══════════════════════════════════════════════════════════════════════════════
Y8 = 17.65
diamond(ax, 11, Y8, 9, 1.0,
        'ENDOSCOPIC + HISTOLOGICAL PATTERN?', fontsize=9)

# ── UC column ────────────────────────────────────────────────────────────────
XUC = 3.5
harrow(ax, 6.5, Y8, XUC+1.8, Y8, label='Continuous\nmucosal', color='#1565C0')

Y8a = 17.65
box(ax, XUC, Y8a-1.3, 5.2, 1.75,
    'ULCERATIVE COLITIS\n──────────────\n'
    '• Continuous from rectum\n'
    '• Erythema, granularity,\n  pseudopolyps\n'
    '• Mucosa / submucosa only\n'
    '• No fistulae or granulomas',
    '#1565C0', fontsize=8, bold=True)

# ── Crohn column ─────────────────────────────────────────────────────────────
XCD = 11
harrow(ax, 11, Y8-0.5, XCD, Y8-1.55, label='', color=C['step'])

box(ax, XCD, Y8-2.05, 5.2, 1.75,
    "CROHN'S DISEASE\n──────────────\n"
    '• Skip lesions, any GI segment\n'
    '• Deep fissures, cobblestoning\n'
    '• Transmural, creeping fat\n'
    '• Granulomas (~35%)',
    '#6A1B9A', fontsize=8, bold=True)

# ── Normal endoscopy column ──────────────────────────────────────────────────
XMC = 18.5
harrow(ax, 15.5, Y8, XMC-1.8, Y8, label='Normal\nappearance', color='#2E7D32')

box(ax, XMC, Y8a-1.3, 5.2, 1.75,
    'MICROSCOPIC COLITIS\n──────────────\n'
    '• Normal mucosa on endoscopy\n'
    '• Biopsy: collagen band >10µm\n  (collagenous) or IEL >20/100\n  (lymphocytic)\n'
    '• Watery non-bloody diarrhea',
    '#2E7D32', fontsize=8, bold=True)

# ══════════════════════════════════════════════════════════════════════════════
# ROW 9  –  Cannot distinguish UC vs Crohn → further imaging
# ══════════════════════════════════════════════════════════════════════════════
Y9 = 14.9
# Arrow from Crohn box down to "indeterminate / need small bowel imaging"
arrow(ax, XCD, Y8-2.93, XCD, Y9+0.55)

box(ax, XCD, Y9, 6.0, 1.0,
    'INDETERMINATE or NEED SMALL BOWEL EVAL?\n'
    '→ MR Enterography (preferred, no radiation)\n'
    '→ CT Enterography (widely available)\n'
    '→ Capsule Endoscopy (rule out stricture first)',
    C['lab'], fontsize=8)

# ══════════════════════════════════════════════════════════════════════════════
# ROW 10  –  Ischemic colitis pathway (side branch from history)
# ══════════════════════════════════════════════════════════════════════════════
# Draw as a side note from the clinical features step
Y10 = 20.0
box(ax, 19.5, Y10, 4.8, 2.2,
    'SUSPECT ISCHEMIC COLITIS\nif:\n'
    '• Elderly + CVD risk factors\n'
    '• Sudden pain → bloody diarrhea\n'
    '• Post-aortic surgery\n──────────────\n'
    '① CT Abdomen/Pelvis with contrast\n'
    '   (thumbprinting, wall thickening)\n'
    '② Flexible sigmoidoscopy / colonoscopy\n'
    '   (when stable, avoid air insufflation)\n'
    '③ Mesenteric angiography (if occlusive)',
    C['warn'], fontsize=7.5)

ax.text(16.8, 25.5, '▶ If ischaemic\n   pattern', fontsize=7.5, color=C['warn'],
        fontweight='bold', ha='center')
ax.annotate('', xy=(19.5, Y10+1.1), xytext=(17.3, Y2-0.6),
            arrowprops=dict(arrowstyle='->', color=C['warn'], lw=1.5,
                            connectionstyle='arc3,rad=0.2'), zorder=2)

# ══════════════════════════════════════════════════════════════════════════════
# ROW 11  –  Final Diagnosis summary bar
# ══════════════════════════════════════════════════════════════════════════════
Y11 = 13.3
box(ax, 11, Y11, 20, 0.75,
    'FINAL DIAGNOSIS  →  Classify, Stage Severity, and Plan Management',
    C['start'], fontsize=10, bold=True)

# 5 diagnosis boxes
DX_Y = 11.9
dx_labels = [
    ('ULCERATIVE\nCOLITIS', '#1565C0'),
    ("CROHN'S\nDISEASE", '#6A1B9A'),
    ('ISCHEMIC\nCOLITIS', '#C62828'),
    ('INFECTIOUS\nCOLITIS', '#2E7D32'),
    ('MICROSCOPIC\nCOLITIS', '#00695C'),
]
dx_x = [2.3, 6.3, 11, 15.7, 19.7]
for (lbl, col), x in zip(dx_labels, dx_x):
    box(ax, x, DX_Y, 3.4, 0.95, lbl, col, fontsize=8.5, bold=True)
    ax.annotate('', xy=(x, DX_Y+0.47), xytext=(11, Y11-0.37),
                arrowprops=dict(arrowstyle='->', color=col, lw=1.2,
                                connectionstyle='arc3,rad=0.0'), zorder=1)

# ══════════════════════════════════════════════════════════════════════════════
# ROW 12  –  Treatment summary per type
# ══════════════════════════════════════════════════════════════════════════════
TX_Y = 10.4
tx_data = [
    ('5-ASA (mild-mod)\nCorticosteroids (acute)\nAzathioprine/6-MP\nBiologics (anti-TNF,\nvedolizumab, ustekinumab)\nSurgery: proctocolectomy', '#BBDEFB', '#0D47A1'),
    ('Corticosteroids\nAzathioprine / MTX\nBiologics (anti-TNF,\nvedolizumab, ustekinumab)\nSurgery: bowel resection\n(not curative)', '#E1BEE7', '#4A148C'),
    ('Conservative (mild):\nIV fluids, bowel rest, O2\nSurgery (severe):\ncolectomy for gangrene\nor perforation', '#FFCDD2', '#B71C1C'),
    ('C. diff: oral vancomycin\nor fidaxomicin\nBacterial: supportive\n± targeted antibiotics\nSevere/recurrent C.diff:\nFMT', '#C8E6C9', '#1B5E20'),
    ('Stop offending drugs\n(NSAIDs, PPIs, SSRIs)\nBudesonide (first line)\nBismuth subsalicylate\nCholestyramine', '#B2DFDB', '#004D40'),
]
tx_x = [2.3, 6.3, 11, 15.7, 19.7]
for (tx, bg, tc), x in zip(tx_data, tx_x):
    box(ax, x, TX_Y, 3.7, 1.9, tx, bg, textcolor=tc, fontsize=7, bold=False)
    arrow(ax, x, DX_Y-0.47, x, TX_Y+0.95)

# Treatment header labels
for lbl, x in zip(['UC Rx', "CD Rx", 'Ischaemic Rx', 'Infectious Rx', 'Microscopic Rx'], tx_x):
    ax.text(x, TX_Y+1.1, lbl, ha='center', va='bottom', fontsize=7.5,
            color='#37474F', fontweight='bold')

# ══════════════════════════════════════════════════════════════════════════════
# LEGEND
# ══════════════════════════════════════════════════════════════════════════════
legend_y = 8.8
ax.text(1.0, legend_y, 'LEGEND:', fontsize=8, fontweight='bold', color='#37474F')
legend_items = [
    (C['start'],    'Start / End / Final step'),
    (C['step'],     'Process / Action'),
    (C['decision'], 'Decision point'),
    (C['lab'],      'Investigations / Labs'),
    (C['dx'],       'Diagnosis'),
    (C['warn'],     'Urgent / Red flag'),
    (C['tx'],       'Treatment / Management'),
]
for i, (col, lbl) in enumerate(legend_items):
    xi = 1.0 + i * 2.95
    p = FancyBboxPatch((xi-0.3, legend_y-0.55), 0.6, 0.4,
                       boxstyle='round,pad=0.05', facecolor=col,
                       edgecolor='white', lw=1)
    ax.add_patch(p)
    ax.text(xi+0.45, legend_y-0.38, lbl, va='center', fontsize=7, color='#37474F')

# ══════════════════════════════════════════════════════════════════════════════
# Footer
# ══════════════════════════════════════════════════════════════════════════════
ax.text(11, 7.9,
        'Sources: Symptom to Diagnosis (4e)  •  Sabiston Textbook of Surgery (21e)  •  '
        'Sleisenger & Fordtran\'s GI & Liver Disease  •  Robbins Pathologic Basis of Disease',
        ha='center', va='center', fontsize=7, color='#78909C', style='italic')

plt.tight_layout(pad=0.5)
plt.savefig('/tmp/workspace/colitis-flowchart/colitis_diagnostic_flowchart.png',
            dpi=180, bbox_inches='tight', facecolor=fig.get_facecolor())
plt.close()
print("Saved successfully.")

Running Command

cd /tmp/workspace/colitis-flowchart && python generate_flowchart.py 2>&1

Running Command

ls -lh /tmp/workspace/colitis-flowchart/colitis_diagnostic_flowchart.png

Loading Image

Reading File

Your diagnostic flowchart is ready:

colitis diagnostic flowchart

Image · PNG

Here is what the flowchart covers, top to bottom:

1. Presentation - Diarrhea ± blood, abdominal pain, urgency/tenesmus

2. History & Physical - Onset duration, blood in stool, recent antibiotics/NSAIDs/travel, weight loss, cardiovascular risk factors, family history of IBD

3. First branch - Acute vs Chronic

Acute path (left): Stool MC&S + C. difficile PCR → if positive = Infectious Colitis + treat; if negative = proceed as chronic
Chronic path (right): Red flags sidebar (toxic megacolon, haemodynamic instability → urgent admission)

4. Initial Labs - CBC, CRP/ESR, albumin, LFTs, B12/folate, TFTs; plus fecal calprotectin, C. diff PCR, stool MC&S, ova & parasites

5. Fecal Calprotectin gate - <50 µg/g = IBD unlikely → IBS/functional; ≥50 µg/g → continue IBD workup

6. Serology - pANCA (UC ~60-70%), ASCA IgG/IgA (Crohn ~50-60%), Anti-OmpC, Anti-CBir1

7. Colonoscopy + Ileoscopy with Biopsy (gold standard) - pattern, extent, ≥6 biopsy sites

8. Endoscopic/Histological branch - Three outcomes:

Continuous mucosal → Ulcerative Colitis
Skip lesions / transmural → Crohn's Disease
Normal endoscopy → Microscopic Colitis (biopsy only)

9. Indeterminate/Small bowel evaluation - MR Enterography (preferred) / CT Enterography / Capsule Endoscopy

10. Ischemic Colitis sidebar - For elderly patients with cardiovascular risk: CT abdomen/pelvis, flexible sigmoidoscopy, mesenteric angiography if occlusive

11-12. Final Diagnosis + Treatment summary - All 5 types with specific management per type (5-ASA, biologics, budesonide, vancomycin/fidaxomicin, surgery thresholds, etc.)

Sources: Symptom to Diagnosis 4e; Sabiston Textbook of Surgery 21e; Sleisenger & Fordtran's GI & Liver Disease; Robbins Pathologic Basis of Disease.

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