Gastroesophageal Reflux Disease (GERD) — Detailed Notes

#!/usr/bin/env python3
"""
GERD Quick-Reference Guide PDF Generator
Uses reportlab with a clean, clinical design.
"""

from reportlab.lib.pagesizes import A4
from reportlab.lib import colors
from reportlab.lib.units import cm, mm
from reportlab.lib.styles import getSampleStyleSheet, ParagraphStyle
from reportlab.lib.enums import TA_LEFT, TA_CENTER, TA_JUSTIFY
from reportlab.platypus import (
    SimpleDocTemplate, Paragraph, Spacer, Table, TableStyle,
    HRFlowable, KeepTogether, PageBreak
)
from reportlab.platypus.flowables import HRFlowable
from reportlab.lib.colors import HexColor

# ── Colour palette ────────────────────────────────────────────────────────────
BLUE_DARK   = HexColor("#1a3a5c")   # dark navy – headings / header
BLUE_MID    = HexColor("#2e6da4")   # medium blue – section bars
BLUE_LIGHT  = HexColor("#dbeaf7")   # pale blue – table alternating rows
RED_ALERT   = HexColor("#c0392b")   # alarm / warning red
GREEN_OK    = HexColor("#1e8449")   # treatment green
ORANGE      = HexColor("#d35400")   # highlights
GREY_TEXT   = HexColor("#2c3e50")   # body text
GREY_LINE   = HexColor("#bdc3c7")
WHITE       = colors.white
BG_HEADER   = BLUE_DARK

PAGE_W, PAGE_H = A4  # 595 x 842 pt
MARGIN = 1.8 * cm

OUTPUT = "/home/daytona/workspace/gerd-guide/GERD_Quick_Reference.pdf"

# ── Styles ────────────────────────────────────────────────────────────────────
def make_styles():
    base = getSampleStyleSheet()
    s = {}

    s["doc_title"] = ParagraphStyle(
        "doc_title",
        fontName="Helvetica-Bold",
        fontSize=22,
        textColor=WHITE,
        alignment=TA_CENTER,
        spaceAfter=2,
        leading=26,
    )
    s["doc_subtitle"] = ParagraphStyle(
        "doc_subtitle",
        fontName="Helvetica",
        fontSize=11,
        textColor=HexColor("#aed6f1"),
        alignment=TA_CENTER,
        spaceAfter=4,
    )
    s["section_header"] = ParagraphStyle(
        "section_header",
        fontName="Helvetica-Bold",
        fontSize=11,
        textColor=WHITE,
        alignment=TA_LEFT,
        spaceBefore=4,
        spaceAfter=4,
        leftIndent=6,
    )
    s["subsection"] = ParagraphStyle(
        "subsection",
        fontName="Helvetica-Bold",
        fontSize=9.5,
        textColor=BLUE_DARK,
        spaceBefore=6,
        spaceAfter=2,
    )
    s["body"] = ParagraphStyle(
        "body",
        fontName="Helvetica",
        fontSize=8.5,
        textColor=GREY_TEXT,
        leading=12,
        spaceAfter=3,
        alignment=TA_JUSTIFY,
    )
    s["bullet"] = ParagraphStyle(
        "bullet",
        fontName="Helvetica",
        fontSize=8.5,
        textColor=GREY_TEXT,
        leading=12,
        leftIndent=10,
        firstLineIndent=-8,
        spaceAfter=2,
    )
    s["small_bold"] = ParagraphStyle(
        "small_bold",
        fontName="Helvetica-Bold",
        fontSize=8,
        textColor=BLUE_DARK,
    )
    s["table_header"] = ParagraphStyle(
        "table_header",
        fontName="Helvetica-Bold",
        fontSize=8,
        textColor=WHITE,
        alignment=TA_CENTER,
    )
    s["table_cell"] = ParagraphStyle(
        "table_cell",
        fontName="Helvetica",
        fontSize=8,
        textColor=GREY_TEXT,
        leading=10,
    )
    s["table_cell_bold"] = ParagraphStyle(
        "table_cell_bold",
        fontName="Helvetica-Bold",
        fontSize=8,
        textColor=GREY_TEXT,
        leading=10,
    )
    s["alert"] = ParagraphStyle(
        "alert",
        fontName="Helvetica-Bold",
        fontSize=8.5,
        textColor=RED_ALERT,
        leading=12,
        leftIndent=10,
        firstLineIndent=-8,
    )
    s["footer"] = ParagraphStyle(
        "footer",
        fontName="Helvetica",
        fontSize=7,
        textColor=HexColor("#7f8c8d"),
        alignment=TA_CENTER,
    )
    return s


# ── Helper builders ───────────────────────────────────────────────────────────
def section_bar(title, s):
    """Returns a coloured section-header bar."""
    p = Paragraph(title, s["section_header"])
    tbl = Table([[p]], colWidths=[PAGE_W - 2 * MARGIN])
    tbl.setStyle(TableStyle([
        ("BACKGROUND", (0, 0), (-1, -1), BLUE_MID),
        ("TOPPADDING",    (0, 0), (-1, -1), 5),
        ("BOTTOMPADDING", (0, 0), (-1, -1), 5),
        ("LEFTPADDING",   (0, 0), (-1, -1), 8),
        ("RIGHTPADDING",  (0, 0), (-1, -1), 8),
        ("ROUNDEDCORNERS", [4]),
    ]))
    return tbl


def two_col_table(data, col_widths, s, header_bg=BLUE_DARK):
    """Styled two-column table with alternating rows."""
    rows = []
    for i, row in enumerate(data):
        rows.append([
            Paragraph(str(row[0]), s["table_cell_bold"] if i == 0 else s["table_cell"]),
            Paragraph(str(row[1]), s["table_header"] if i == 0 else s["table_cell"]),
        ])
    style = [
        ("BACKGROUND",    (0, 0), (-1,  0), header_bg),
        ("TEXTCOLOR",     (0, 0), (-1,  0), WHITE),
        ("FONTNAME",      (0, 0), (-1,  0), "Helvetica-Bold"),
        ("FONTSIZE",      (0, 0), (-1,  0), 8),
        ("ALIGN",         (0, 0), (-1,  0), "CENTER"),
        ("TOPPADDING",    (0, 0), (-1, -1), 4),
        ("BOTTOMPADDING", (0, 0), (-1, -1), 4),
        ("LEFTPADDING",   (0, 0), (-1, -1), 6),
        ("RIGHTPADDING",  (0, 0), (-1, -1), 6),
        ("GRID",          (0, 0), (-1, -1), 0.4, GREY_LINE),
        ("VALIGN",        (0, 0), (-1, -1), "MIDDLE"),
    ]
    for i in range(1, len(rows)):
        bg = BLUE_LIGHT if i % 2 == 0 else WHITE
        style.append(("BACKGROUND", (0, i), (-1, i), bg))
    tbl = Table(rows, colWidths=col_widths)
    tbl.setStyle(TableStyle(style))
    return tbl


def three_col_table(data, col_widths, s, header_bg=BLUE_DARK):
    rows = []
    for i, row in enumerate(data):
        if i == 0:
            rows.append([Paragraph(str(c), s["table_header"]) for c in row])
        else:
            rows.append([Paragraph(str(c), s["table_cell"]) for c in row])
    style = [
        ("BACKGROUND",    (0, 0), (-1,  0), header_bg),
        ("TEXTCOLOR",     (0, 0), (-1,  0), WHITE),
        ("FONTNAME",      (0, 0), (-1,  0), "Helvetica-Bold"),
        ("FONTSIZE",      (0, 0), (-1,  0), 8),
        ("ALIGN",         (0, 0), (-1,  0), "CENTER"),
        ("TOPPADDING",    (0, 0), (-1, -1), 4),
        ("BOTTOMPADDING", (0, 0), (-1, -1), 4),
        ("LEFTPADDING",   (0, 0), (-1, -1), 6),
        ("RIGHTPADDING",  (0, 0), (-1, -1), 6),
        ("GRID",          (0, 0), (-1, -1), 0.4, GREY_LINE),
        ("VALIGN",        (0, 0), (-1, -1), "MIDDLE"),
    ]
    for i in range(1, len(rows)):
        bg = BLUE_LIGHT if i % 2 == 0 else WHITE
        style.append(("BACKGROUND", (0, i), (-1, i), bg))
    tbl = Table(rows, colWidths=col_widths)
    tbl.setStyle(TableStyle(style))
    return tbl


def alert_box(text_lines, s):
    """Red-bordered alert box."""
    content = [Paragraph(f"⚠  {line}", s["alert"]) for line in text_lines]
    inner = Table([[c] for c in content], colWidths=[PAGE_W - 2*MARGIN - 20])
    inner.setStyle(TableStyle([
        ("TOPPADDING",    (0, 0), (-1, -1), 2),
        ("BOTTOMPADDING", (0, 0), (-1, -1), 2),
        ("LEFTPADDING",   (0, 0), (-1, -1), 4),
    ]))
    outer = Table([[inner]], colWidths=[PAGE_W - 2*MARGIN])
    outer.setStyle(TableStyle([
        ("BOX",           (0, 0), (-1, -1), 1.5, RED_ALERT),
        ("BACKGROUND",    (0, 0), (-1, -1), HexColor("#fdf2f2")),
        ("TOPPADDING",    (0, 0), (-1, -1), 6),
        ("BOTTOMPADDING", (0, 0), (-1, -1), 6),
        ("LEFTPADDING",   (0, 0), (-1, -1), 8),
        ("RIGHTPADDING",  (0, 0), (-1, -1), 8),
    ]))
    return outer


def info_box(text_lines, s, bg=HexColor("#eafaf1"), border=GREEN_OK):
    content = [Paragraph(f"✓  {line}", s["bullet"]) for line in text_lines]
    inner = Table([[c] for c in content], colWidths=[PAGE_W - 2*MARGIN - 20])
    inner.setStyle(TableStyle([
        ("TOPPADDING",    (0, 0), (-1, -1), 2),
        ("BOTTOMPADDING", (0, 0), (-1, -1), 2),
    ]))
    outer = Table([[inner]], colWidths=[PAGE_W - 2*MARGIN])
    outer.setStyle(TableStyle([
        ("BOX",           (0, 0), (-1, -1), 1.5, border),
        ("BACKGROUND",    (0, 0), (-1, -1), bg),
        ("TOPPADDING",    (0, 0), (-1, -1), 6),
        ("BOTTOMPADDING", (0, 0), (-1, -1), 6),
        ("LEFTPADDING",   (0, 0), (-1, -1), 8),
        ("RIGHTPADDING",  (0, 0), (-1, -1), 8),
    ]))
    return outer


# ── Header / footer callbacks ─────────────────────────────────────────────────
def on_first_page(canvas, doc):
    w, h = A4
    # Header banner
    canvas.setFillColor(BG_HEADER)
    canvas.rect(0, h - 80, w, 80, fill=1, stroke=0)
    # Title
    canvas.setFillColor(WHITE)
    canvas.setFont("Helvetica-Bold", 22)
    canvas.drawCentredString(w / 2, h - 38, "GASTROESOPHAGEAL REFLUX DISEASE (GERD)")
    canvas.setFont("Helvetica", 11)
    canvas.setFillColor(HexColor("#aed6f1"))
    canvas.drawCentredString(w / 2, h - 56, "Quick-Reference Management Guide")
    canvas.setFont("Helvetica", 9)
    canvas.drawCentredString(w / 2, h - 70, "Based on Goldman-Cecil Medicine | Robbins Pathology | Yamada's Gastroenterology | Schwartz's Surgery")
    # Footer
    canvas.setFillColor(HexColor("#7f8c8d"))
    canvas.setFont("Helvetica", 7)
    canvas.drawCentredString(w / 2, 18, f"Page {doc.page}  |  GERD Quick-Reference Guide  |  For educational use only")
    canvas.setStrokeColor(GREY_LINE)
    canvas.line(MARGIN, 28, w - MARGIN, 28)


def on_later_pages(canvas, doc):
    w, h = A4
    # Slim header bar
    canvas.setFillColor(BLUE_MID)
    canvas.rect(0, h - 28, w, 28, fill=1, stroke=0)
    canvas.setFillColor(WHITE)
    canvas.setFont("Helvetica-Bold", 9)
    canvas.drawCentredString(w / 2, h - 16, "GERD Quick-Reference Guide")
    # Footer
    canvas.setFillColor(HexColor("#7f8c8d"))
    canvas.setFont("Helvetica", 7)
    canvas.drawCentredString(w / 2, 18, f"Page {doc.page}  |  GERD Quick-Reference Guide  |  For educational use only")
    canvas.setStrokeColor(GREY_LINE)
    canvas.line(MARGIN, 28, w - MARGIN, 28)


# ── Main content builder ──────────────────────────────────────────────────────
def build_story(s):
    story = []
    W = PAGE_W - 2 * MARGIN   # usable width

    def sp(n=6): return Spacer(1, n)
    def hr(): return HRFlowable(width=W, thickness=0.5, color=GREY_LINE, spaceAfter=4, spaceBefore=4)

    # ── PAGE 1 ───────────────────────────────────────────────────────────────
    story.append(sp(10))

    # ── 1. DEFINITION & EPIDEMIOLOGY ─────────────────────────────────────────
    story.append(section_bar("1.  DEFINITION & EPIDEMIOLOGY", s))
    story.append(sp(4))
    story.append(Paragraph(
        "GERD is a <b>chronic disorder</b> in which gastric contents (acid, pepsin, bile) reflux "
        "into the esophagus, causing mucosal injury and/or troublesome symptoms — distinguished "
        "from physiological GER by its clinical impact.",
        s["body"]
    ))
    epi_data = [
        ["Parameter", "Key Figure"],
        ["Global prevalence (Western)", "20–40%  |  East Asia: &lt;10%"],
        ["US annual outpatient visits", "Most common GI outpatient diagnosis"],
        ["Obesity (BMI &gt;30) OR for GERD", "1.94 vs. normal weight"],
        ["GERD → Barrett's esophagus OR", "4.0 (95% CI 1.4–11.1)"],
        ["PPI symptom relief rate", "Up to 90% of patients"],
    ]
    story.append(two_col_table(epi_data, [W*0.45, W*0.55], s))
    story.append(sp(8))

    # ── 2. RISK FACTORS ───────────────────────────────────────────────────────
    story.append(section_bar("2.  RISK FACTORS / CAUSES", s))
    story.append(sp(4))
    rf_data = [
        ["Category", "Specific Factors"],
        ["Lifestyle", "Obesity (esp. abdominal), smoking, alcohol, caffeine, fatty/spicy foods, large late meals"],
        ["Anatomical", "Hiatal hernia (sliding &gt;95%), short intraabdominal esophageal segment"],
        ["Physiological", "Pregnancy, delayed gastric emptying, increased gastric volume/acid secretion"],
        ["Drugs", "Anticholinergics, CCBs, theophylline, beta-agonists, nitrates, NSAIDs, bisphosphonates"],
        ["Systemic disease", "Scleroderma, CREST syndrome (oesophageal dysmotility), Zollinger-Ellison syndrome"],
        ["Other", "CNS depressants, nasogastric tubes, post-surgical (e.g. Heller myotomy)"],
    ]
    story.append(two_col_table(rf_data, [W*0.25, W*0.75], s))
    story.append(sp(8))

    # ── 3. PATHOPHYSIOLOGY ───────────────────────────────────────────────────
    story.append(section_bar("3.  PATHOPHYSIOLOGY", s))
    story.append(sp(4))
    story.append(Paragraph("<b>Three-layer failure model:</b>", s["subsection"]))

    patho_data = [
        ["Mechanism", "Detail"],
        ["Transient LES Relaxation (tLESR) — PRIMARY",
         "Vagally-mediated; triggered by gastric distension; unaccompanied by peristalsis → prolonged acid exposure"],
        ["Decreased basal LES pressure",
         "Drugs, alcohol, tobacco, obesity, scleroderma → persistent LES incompetence"],
        ["Hiatal hernia",
         "Displaces GEJ into thorax; disrupts crural diaphragm augmentation; creates acid reservoir above diaphragm"],
        ["Impaired esophageal clearance",
         "Weak peristalsis → prolonged acid contact; reduced saliva (bicarbonate) — worsened by smoking"],
        ["Increased intraabdominal pressure",
         "Obesity, pregnancy, coughing, straining, bending → overcomes LES barrier transiently"],
        ["Mucosal defence failure",
         "Breakdown of tight junctions, mucus layer, bicarbonate secretion → intracellular acidification → inflammation"],
    ]
    story.append(two_col_table(patho_data, [W*0.35, W*0.65], s))
    story.append(sp(4))
    story.append(Paragraph("<b>Injury cascade:</b>  Acid exposure → intercellular oedema → basal hyperplasia / papillary elongation "
                           "→ eosinophil infiltration → erosions / ulcers → fibrosis (stricture) → columnar metaplasia "
                           "(Barrett's) → adenocarcinoma", s["body"]))
    story.append(sp(8))

    # ── 4. SIGNS & SYMPTOMS ──────────────────────────────────────────────────
    story.append(section_bar("4.  SIGNS & SYMPTOMS", s))
    story.append(sp(4))

    # Two side-by-side mini tables
    typical_data = [
        ["Typical (Esophageal)", "Description"],
        ["Heartburn", "Substernal burning, postprandial / supine, worsened bending forward"],
        ["Acid regurgitation", "Sour/bitter taste reaching pharynx or mouth"],
        ["Waterbrash", "Sudden flood of saliva (reflex hypersalivation)"],
        ["Belching", "Air swallowing / gas reflux"],
        ["Dysphagia*", "Solid food sticking — may signal stricture (alarm)"],
        ["Odynophagia*", "Painful swallowing — suggests ulceration"],
        ["Chest pain", "May mimic cardiac angina; exclude cardiac cause first"],
    ]
    atypical_data = [
        ["Extraesophageal (Atypical)", "Mechanism"],
        ["Chronic cough", "Microaspiration / vagal reflex"],
        ["Laryngitis / hoarseness", "Acid injury to larynx"],
        ["Asthma exacerbation", "Vagal reflex bronchospasm / aspiration"],
        ["Dental enamel erosion", "Acid dissolves palatal enamel (irreversible)"],
        ["Sinusitis / otitis media", "Proposed — less clear causality"],
        ["Pharyngitis / throat clearing", "Laryngopharyngeal reflux"],
        ["Aspiration pneumonia", "Microaspiration of gastric contents"],
    ]

    t1 = two_col_table(typical_data, [W*0.3, W*0.2], s)
    t2 = two_col_table(atypical_data, [W*0.3, W*0.2], s)
    side_by_side = Table([[t1, sp(6), t2]], colWidths=[W*0.48, 6, W*0.48])
    side_by_side.setStyle(TableStyle([("VALIGN", (0,0), (-1,-1), "TOP")]))
    story.append(side_by_side)
    story.append(sp(4))
    story.append(Paragraph(
        "<i>*Severity of symptoms does NOT correlate with degree of histologic damage (Robbins Pathology).</i>",
        s["body"]
    ))
    story.append(sp(6))

    # Alarm features
    story.append(alert_box([
        "ALARM FEATURES — require urgent endoscopy / investigation:",
        "Dysphagia or odynophagia  |  Unintentional weight loss  |  GI bleeding (haematemesis / melaena)",
        "Iron-deficiency anaemia  |  Persistent symptoms despite 4–8 weeks PPI  |  Age >45, new-onset symptoms",
    ], s))
    story.append(sp(8))

    # ── COMPLICATIONS ─────────────────────────────────────────────────────────
    story.append(section_bar("5.  COMPLICATIONS", s))
    story.append(sp(4))
    comp_data = [
        ["Complication", "Features", "Management Overview"],
        ["Erosive Esophagitis\n(LA Grade A–D)",
         "Grade A: &lt;5 mm breaks; Grade D: &gt;75% circumference with ulcers",
         "PPI therapy; heal in 4–8 weeks"],
        ["Peptic Stricture",
         "Progressive solid-food dysphagia; fibrous narrowing distal esophagus",
         "Endoscopic dilation (balloon/bougie) + long-term PPI"],
        ["Barrett's Esophagus",
         "Columnar (intestinal) metaplasia; salmon-pink mucosa on endoscopy; OR 4.0 with obesity",
         "Surveillance EGD q3–5 yr; RFA / cryoablation for dysplasia"],
        ["Esophageal Adenocarcinoma",
         "Arises from Barrett's high-grade dysplasia; RR 4.8 in obese; dysphagia + weight loss",
         "EMR (early) / esophagectomy + neo-adjuvant CRT"],
        ["Aspiration Pneumonia",
         "Nocturnal microaspiration; recurrent lower lobe infiltrates",
         "Optimize acid suppression; consider antireflux surgery"],
    ]
    cw = [W*0.23, W*0.42, W*0.35]
    story.append(three_col_table(comp_data, cw, s))
    story.append(sp(10))

    # ── PAGE 2 ───────────────────────────────────────────────────────────────
    story.append(PageBreak())

    # ── 6. INVESTIGATIONS ────────────────────────────────────────────────────
    story.append(sp(10))
    story.append(section_bar("6.  INVESTIGATIONS", s))
    story.append(sp(4))
    story.append(Paragraph(
        "<b>Clinical diagnosis is sufficient</b> when classic heartburn + regurgitation respond to empiric PPI therapy. "
        "Investigate when alarm features are present, symptoms are atypical, or treatment fails after 4–8 weeks.",
        s["body"]
    ))
    story.append(sp(4))
    inv_data = [
        ["Investigation", "Indication", "Key Findings / Notes"],
        ["Empiric PPI Trial\n(4–8 weeks)",
         "Typical symptoms, no alarm features",
         "~70% sensitivity; response supports GERD diagnosis"],
        ["Upper GI Endoscopy (EGD)",
         "Alarm symptoms; PPI failure; Barrett's screening",
         "Erosions, ulcers, stricture, Barrett's; ~2/3 GERD pts have NORMAL endoscopy"],
        ["24-hr Ambulatory pH\nMonitoring",
         "EGD normal + symptoms persist (OFF PPI)",
         "Gold standard for acid exposure; pH &lt;4 for &gt;4–6% = abnormal; correlates symptom-reflux"],
        ["48–96 hr Wireless pH\nCapsule (Bravo)",
         "Better tolerated alternative to nasal catheter",
         "Higher diagnostic yield; day-to-day variation captured"],
        ["Combined Impedance-pH\nMonitoring (MII-pH)",
         "Persistent symptoms ON PPI",
         "Detects acid AND non-acid reflux; best for PPI-refractory GERD"],
        ["High-Resolution\nManometry (HRM)",
         "Pre-surgical evaluation; exclude achalasia",
         "Measures LES pressure + peristalsis; identifies poor motility (risk for wrap dysphagia)"],
        ["Barium Swallow",
         "Structural assessment (stricture, hernia)\nPaediatric workup",
         "NOT recommended for routine uncomplicated GERD; limited sensitivity/specificity"],
        ["Gastric Emptying Scan\n(Tc-99m)",
         "Suspected gastroparesis contributing to GERD",
         "Normal: 50% emptied at 60 min, ~80% at 90 min"],
    ]
    story.append(three_col_table(inv_data, [W*0.24, W*0.31, W*0.45], s))
    story.append(sp(4))
    story.append(Paragraph(
        "<b>Histology on biopsy:</b>  Basal zone hyperplasia | Papillary elongation | Intercellular oedema "
        "| Eosinophil infiltration | 'Balloon' cells | Erosions (severe). "
        "Biopsies should be taken &gt;2 cm above GEJ. Changes most prominent in distal 8–10 cm.",
        s["body"]
    ))
    story.append(sp(8))

    # ── 7. TREATMENT ─────────────────────────────────────────────────────────
    story.append(section_bar("7.  TREATMENT — STEPWISE APPROACH", s))
    story.append(sp(4))

    # Step 1 – Lifestyle
    story.append(Paragraph("STEP 1  —  Lifestyle Modifications", s["subsection"]))
    story.append(info_box([
        "Weight loss (strongest evidence — reduces intraabdominal pressure and gastric acid production)",
        "Elevate head of bed 6–8 inches / wedge pillow — for nocturnal heartburn",
        "Avoid meals &lt;3 hours before lying down",
        "Avoid triggers: alcohol, caffeine, spicy/fatty foods, chocolate, peppermint, carbonated drinks",
        "Small, frequent meals; eat slowly",
        "Smoking cessation (reduces LES tone + impairs mucosal defence)",
        "Avoid tight abdominal clothing",
        "Review medications that lower LES tone (CCBs, nitrates, anticholinergics)",
    ], s))
    story.append(sp(6))

    # Step 2 – Pharmacotherapy
    story.append(Paragraph("STEP 2  —  Pharmacological Treatment", s["subsection"]))
    story.append(sp(3))

    drug_data = [
        ["Drug Class", "Agent / Dose", "Mechanism", "Role / Notes"],
        ["Antacids",
         "Al/Mg hydroxide 15 mL QID\n1 hr after meals + bedtime",
         "Neutralise gastric acid; transiently increase LES pressure",
         "Rapid but short-lived relief; mild / infrequent GERD; NOT for maintenance"],
        ["Alginates\n(Gaviscon)",
         "2–4 tablets QID + bedtime\n(Al(OH)3 + NaHCO3 + alginic acid)",
         "Forms viscous raft on gastric surface as mechanical barrier; buffers acid",
         "Post-prandial heartburn; safe in pregnancy; adjunct to PPI"],
        ["H2-Receptor\nAntagonists",
         "Famotidine 20–40 mg BD\nRanitidine 150 mg BD–QID\nCimetidine 400 mg BD\nNizatidine 150 mg BD",
         "Block parietal-cell H2 receptors → reduce acid secretion",
         "Second-line; useful for nocturnal breakthrough; subject to tachyphylaxis; inferior to PPIs for esophagitis healing"],
        ["Proton Pump\nInhibitors (PPIs)\n— FIRST-LINE",
         "Omeprazole 20–40 mg/day\nLansoprazole 15–30 mg/day\nPantoprazole 40 mg/day\nEsomeprazole 20–40 mg/day\nRabeprazole 20 mg/day\nDexlansoprazole 30–60 mg/day",
         "Irreversibly inhibit H+/K+-ATPase on parietal-cell canalicular membrane; activated in acidic environment",
         "CORNERSTONE of treatment. Take 30 min before meals. Superior to H2RAs. Relief in up to 90%. Titrate to lowest effective dose for maintenance."],
        ["Long-term PPI\nAdverse Effects",
         "— (monitoring required)",
         "Prolonged acid suppression",
         "Vit B12 deficiency | C. difficile infection | Community pneumonia | Hip fracture | Hypomagnesaemia | SIBO | Diabetes (weak signal)"],
        ["Prokinetics\n(NOT routinely used)",
         "Metoclopramide",
         "Increases LES pressure + gastric emptying",
         "No high-quality RCT data; risk of tardive dyskinesia; NOT recommended as monotherapy or adjunct"],
    ]
    story.append(three_col_table(drug_data, [W*0.16, W*0.24, W*0.28, W*0.32], s))
    story.append(sp(6))

    # Step 3 – Endoscopic
    story.append(Paragraph("STEP 3  —  Endoscopic / Minimally Invasive Therapies (selected patients)", s["subsection"]))
    endo_data = [
        ["Procedure", "Description", "Efficacy"],
        ["Transoral Incisionless\nFundoplication (TIF)",
         "Endoscopic reconstruction of gastroesophageal valve; no incision",
         "Normalises acid exposure in ~50%; suitable for small hernias"],
        ["Radiofrequency Ablation\n(Stretta)",
         "RF energy delivered to LES/cardia; improves barrier function via fibrosis",
         "Modest symptom improvement; reduces PPI use"],
        ["LINX (Magnetic\nSphincteR Augmentation)",
         "Ring of magnetic beads implanted laparoscopically around LES",
         "Prevents reflux while allowing swallowing; reversible; avoid in large hernias"],
    ]
    story.append(three_col_table(endo_data, [W*0.25, W*0.42, W*0.33], s))
    story.append(sp(6))

    # Step 4 – Surgery
    story.append(Paragraph("STEP 4  —  Surgical Treatment (Anti-reflux Surgery)", s["subsection"]))
    story.append(sp(3))
    surg_ind = [
        "Documented esophagitis not responding to or intolerant of PPIs",
        "Persistent voluminous regurgitation despite PPI (PPIs control acid, NOT volume)",
        "Patient preference to avoid lifelong medication",
        "Complications — symptomatic hiatal hernia, peptic stricture",
        "Pre-Barrett's dysplasia management (selected cases)",
    ]
    story.append(info_box(surg_ind, s, bg=HexColor("#eaf2fb"), border=BLUE_MID))
    story.append(sp(4))

    surg_data = [
        ["Procedure", "Description", "Outcomes / Notes"],
        ["Nissen Fundoplication\n(360° wrap) — GOLD STANDARD",
         "Fundus wrapped 360° around distal esophagus; laparoscopic approach standard",
         "Equivalent to PPIs for esophagitis healing; SUPERIOR for persistent regurgitation; 15–20% recurrence"],
        ["Toupet Fundoplication\n(270° posterior wrap)",
         "Partial posterior wrap; preferred when esophageal motility is poor",
         "Lower dysphagia rate than Nissen; similar reflux control"],
        ["Dor Fundoplication\n(270° anterior wrap)",
         "Partial anterior wrap; often used after Heller myotomy for achalasia",
         "Reduces post-myotomy reflux"],
        ["Complications of Surgery",
         "Dysphagia (tight wrap), gas-bloat syndrome, vagal nerve injury, diarrhoea",
         "Require careful patient selection + meticulous technique"],
    ]
    story.append(three_col_table(surg_data, [W*0.26, W*0.40, W*0.34], s))
    story.append(sp(8))

    # ── 8. MANAGEMENT ALGORITHM ──────────────────────────────────────────────
    story.append(section_bar("8.  MANAGEMENT ALGORITHM (SUMMARY FLOWCHART)", s))
    story.append(sp(4))

    algo_rows = [
        ["Typical symptoms\n(heartburn + regurgitation)",
         "→",
         "Empiric PPI\n(4–8 wks once daily,\n30 min before meals)\n+ Lifestyle measures",
         "→",
         "Symptoms resolve?\nYes → Lowest-dose\nmaintenance or PRN\nNo → Step up"],
        ["Alarm features\npresent or PPI failure",
         "→",
         "Upper GI Endoscopy\n(EGD)",
         "→",
         "Erosive esophagitis →\nIntensify PPI (BD dose)\nBarrett's → Surveillance\nNormal → pH monitoring"],
        ["PPI-refractory\n(symptoms persist on PPI)",
         "→",
         "MII-pH monitoring ON PPI\n(combined impedance-pH)",
         "→",
         "Acid breakthrough →\nDose adjust / switch PPI\nNon-acid reflux →\nSurgical referral"],
        ["Surgical candidate\n(regurgitation dominant\nor PPI intolerant)",
         "→",
         "Manometry +\npH testing OFF PPI",
         "→",
         "Laparoscopic Nissen\nFundoplication\n(or Toupet if poor motility)"],
    ]

    algo_col = [W*0.21, W*0.04, W*0.26, W*0.04, W*0.45]
    algo_table_data = []
    for row in algo_rows:
        tr = []
        for i, cell in enumerate(row):
            if i in (1, 3):
                tr.append(Paragraph("<b>→</b>", ParagraphStyle("arr", fontName="Helvetica-Bold",
                          fontSize=14, textColor=BLUE_MID, alignment=TA_CENTER)))
            elif i == 0:
                tr.append(Paragraph(cell, ParagraphStyle("box0", fontName="Helvetica-Bold",
                          fontSize=7.5, textColor=BLUE_DARK, alignment=TA_CENTER, leading=10)))
            elif i == 2:
                tr.append(Paragraph(cell, ParagraphStyle("box2", fontName="Helvetica",
                          fontSize=7.5, textColor=GREY_TEXT, alignment=TA_CENTER, leading=10)))
            else:
                tr.append(Paragraph(cell, ParagraphStyle("box4", fontName="Helvetica",
                          fontSize=7.5, textColor=GREY_TEXT, alignment=TA_LEFT, leading=10)))
        algo_table_data.append(tr)

    algo_tbl = Table(algo_table_data, colWidths=algo_col, rowHeights=None)
    algo_style = [
        ("VALIGN",        (0, 0), (-1, -1), "MIDDLE"),
        ("TOPPADDING",    (0, 0), (-1, -1), 6),
        ("BOTTOMPADDING", (0, 0), (-1, -1), 6),
        ("LEFTPADDING",   (0, 0), (-1, -1), 6),
        ("RIGHTPADDING",  (0, 0), (-1, -1), 6),
        ("GRID",          (0, 0), (0, -1),  0.5, GREY_LINE),
        ("GRID",          (2, 0), (2, -1),  0.5, GREY_LINE),
        ("GRID",          (4, 0), (4, -1),  0.5, GREY_LINE),
        ("ROWBACKGROUNDS", (0, 0), (-1, -1), [BLUE_LIGHT, WHITE, BLUE_LIGHT, WHITE]),
    ]
    for r in range(len(algo_rows)):
        bg = BLUE_LIGHT if r % 2 == 0 else WHITE
        algo_style += [
            ("BACKGROUND", (0, r), (0, r), HexColor("#dbeef9")),
            ("BACKGROUND", (2, r), (2, r), HexColor("#eafaf1")),
            ("BACKGROUND", (4, r), (4, r), bg),
        ]
    algo_tbl.setStyle(TableStyle(algo_style))
    story.append(algo_tbl)
    story.append(sp(8))

    # ── 9. SPECIAL POPULATIONS ───────────────────────────────────────────────
    story.append(section_bar("9.  SPECIAL POPULATIONS", s))
    story.append(sp(4))
    sp_data = [
        ["Population", "Key Considerations"],
        ["Pregnancy",
         "First-line: antacids + alginates (safest). H2RAs (famotidine) if needed. PPI: generally avoid in T1; "
         "use only if clearly indicated in T2/T3. Positional measures essential."],
        ["Elderly",
         "Atypical presentation — regurgitation, dyspepsia, noncardiac chest pain rather than heartburn. "
         "Higher risk of complications (strictures, Barrett's). Caution with long-term PPI (fracture, B12 deficiency)."],
        ["Paediatric / Infants",
         "Physiological GER normal until 6–12 months. GERD diagnosed with failure to thrive, apnea, recurrent aspiration. "
         "Formula thickening + positioning first; H2RA/PPI if needed; Nissen fundoplication for severe/refractory cases."],
        ["Scleroderma / CTD",
         "Profound esophageal dysmotility; high aspiration risk. PPI backbone; avoid fundoplication "
         "(complete wrap worsens dysphagia); partial wrap or no surgery."],
        ["Non-erosive Reflux\nDisease (NERD)",
         "~2/3 of GERD patients have normal EGD. Diagnose with pH monitoring. "
         "Respond less well to PPIs; consider MII-pH; exclude functional heartburn."],
    ]
    story.append(two_col_table(sp_data, [W*0.22, W*0.78], s))
    story.append(sp(8))

    # ── 10. PROGNOSIS ─────────────────────────────────────────────────────────
    story.append(section_bar("10.  PROGNOSIS", s))
    story.append(sp(4))
    story.append(Paragraph(
        "The majority of patients with GERD do well with conservative antireflux measures and PPI therapy. "
        "Long-term maintenance therapy is often required for erosive esophagitis. When anti-reflux surgery is performed "
        "in appropriately selected patients, the outcome is usually excellent. Patients with Barrett's esophagus "
        "require endoscopic surveillance; ablative therapy for dysplasia has excellent results. "
        "The overall 5-year survival for esophageal adenocarcinoma detected early (T1) approaches 80%, "
        "underlining the importance of Barrett's surveillance.",
        s["body"]
    ))
    story.append(sp(6))

    # Sources
    story.append(hr())
    story.append(Paragraph(
        "<b>Sources:</b>  Goldman-Cecil Medicine (26th ed.) | Robbins Pathologic Basis of Disease (10th ed.) | "
        "Yamada's Textbook of Gastroenterology (7th ed.) | Clinical Gastrointestinal Endoscopy (3rd ed.) | "
        "Schwartz's Principles of Surgery (11th ed.) | Sabiston Textbook of Surgery",
        s["footer"]
    ))

    return story


# ── Entry point ───────────────────────────────────────────────────────────────
def main():
    s = make_styles()

    doc = SimpleDocTemplate(
        OUTPUT,
        pagesize=A4,
        leftMargin=MARGIN,
        rightMargin=MARGIN,
        topMargin=88,          # room for header on p1
        bottomMargin=36,
    )

    story = build_story(s)

    doc.build(
        story,
        onFirstPage=on_first_page,
        onLaterPages=on_later_pages,
    )
    print(f"PDF saved to: {OUTPUT}")


if __name__ == "__main__":
    main()